Mental Maths - Group 1 and 2 27.4.20 (Fractions of amounts) Dear Parents, This week during mental maths sessions, the children will be learning to calculate mentally, fractions of given amounts. In order to do this the children need to understand the link between fractions and division. They need to understand that in order to find a fraction of an amount, they must divide. For example if you are asked to work out half of a given amount, you would divide by 2, if you were asked to work out a third of a specified amount, you would divide by 3 and so on … The children also need to know their table/division facts in order to quickly work out fractions of different amounts in their head without pencil and paper to help them. Please ask your child the following types of questions each day so as to develop their ability to do this. You could ask: What is half of 18? (18 divided by 2 = 9) What is one third of 30? (30 divided by 3 = 10) What is a quarter of 32? (32 divided by 4 = 8) What is a fifth of 45? (45 divided by 5 = 9) What is one sixth of 48? (48 divided by 6 = 8) What is one seventh of 63? (63 divided by 7 = 9) What is one eighth of 72? (72 divided by 8 = 9) What is one ninth of 81? (81 divided by 9 = 9) What is one tenth of 50? (50 divided by 10 = 5) Children are learning that a fraction is an EQUAL PART of a whole object or whole amount. Mental maths activities should be carried out every day for 10-15 minutes
Transcript
Mental Maths - Group 1 and 2
27.4.20
(Fractions of amounts)
Dear Parents,
This week during mental maths sessions, the children will be
learning to calculate mentally, fractions of given amounts. In order to do this
the children need to understand the link between fractions and division. They
need to understand that in order to find a fraction of an amount, they must
divide. For example if you are asked to work out half of a given amount, you
would divide by 2, if you were asked to work out a third of a specified amount,
you would divide by 3 and so on …
The children also need to know their table/division facts in order to quickly
work out fractions of different amounts in their head without pencil and paper
to help them. Please ask your child the following types of questions each day so
as to develop their ability to do this.
You could ask:
What is half of 18? (18 divided by 2 = 9)
What is one third of 30? (30 divided by 3 = 10)
What is a quarter of 32? (32 divided by 4 = 8)
What is a fifth of 45? (45 divided by 5 = 9)
What is one sixth of 48? (48 divided by 6 = 8)
What is one seventh of 63? (63 divided by 7 = 9)
What is one eighth of 72? (72 divided by 8 = 9)
What is one ninth of 81? (81 divided by 9 = 9)
What is one tenth of 50? (50 divided by 10 = 5)
Children are learning that a fraction is an EQUAL PART of a whole
object or whole amount.
Mental maths activities should be carried out every day for 10-15 minutes
As well as asking the above questions, you should also ask your child to calculate
Finding a fraction of an amount/quantity Here is the fool proof method for find a FRACTION of an AMOUNT, also known as QUANTITY.
Look through the example, and follow each stage with the steps below.
Find ¾ of £28 28 ÷4 = 7 7 x 3 = £21
Step one: Find the number you are finding a fraction of and circle it.
Step two: Find the denominator (bottom) of the fraction you are finding, and underline this.
Step three: DIVIDE the circled number (the quantity) by the denominator. 28 ÷4 = 7
Step four: Now take this value and multiply by the numerator (top) in your fraction.7 x 3
Step five: You have now found a fraction of a quantity, underline this, it’s your answer! = £21
Follow the same five steps to answer the next set of questions.
Find ⅝of 48cm 48 ÷8 = 7 7 x 5 = cm
Find 74 of 63kg 48 ÷ = 7 x = 2 kg
Find 92 of £72 48 ÷ = 7 7 x = 21
Find 83 of 96m 48 ÷ = 7 7 x = 21
Find 125 of £60 48 ÷ = 7 7 x = 21
Find 117 of 66m 48 ÷ = 7 7 x = 21
Find 87 of 56kg 48 ÷ = 7 7 x = 21
1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11.
LO: To find fractions of numbers or amounts (e)
Look at these trays of cakes. You buy a fraction of each tray or cakes. Work out how many cakes you buy. To find ½ divide by 2, to find ¼ divide by 4, to find 1/5 divide by 5. 1. 2.
¼ of 16 = ¾ of 16 = ¼ of 8 = ¾ of 8 = 3. 4.
1/5 of 10 = 3/5 of 10= 1/5 of 15 = 4/5 of 15 = 5. 6.
1/3 of 9 = 2/3 of 9 = 1/5 of 20 = 3/5 of 20 = 7. 8. 1/3 of 18 = 2/3 of 18 = ¼ of 12 = ¾ of 12 =
NOW try this: 9. find 2/5 of 25 10. find ¾ of 44 = 11. find ¾ of 16 12. find 3/5 of 65 13. find 3/5 of 35 14. find 4/5 of 80 15. find 2/3 of 18 16. find 2/3 of 33 17. find 2/3 of 27 18. find 4/10 of 20 19. find 7/10 of 50 20 find 6/10 of 90 21. find 3/10 of 20 22. find ¾ of 12 23. find 3/5 of 85
1. In a bag of marbles, there are 86 marbles. ½ are blue. How many blue
marbles are there?
2. On a bus there are 124 passengers. ½ are children. How many children are there?
3. I win £36 on the lottery, but give 1/3 away – how much do I give away?
4. In the classroom there are 45 children. 1/3 like maths. How many children like maths?
5. I threw away 148 Kg of rubbish, but recycled 1/4 of it. How much rubbish did I recycle?
6. A shark chases 244 fish, and eats 3/4 of them – how many does it eat?
7. There is 60ml of pop in my bottle, but I spill 2/3 of it – how much do I spill?
8. I am reading a book which is 55 pages long. I have read 2/5 of it. How many pages have I read?
9. I ate 24 smarties, which was 1/4 of the packet. How many were in the packet to start with?
Can you write story problems for these sums, and then work out the answers?
a) ½ of 120. b) 1/3 of 27. c) ¼ of 164.
Comparing Fractions with the Same Denominator
Use the < or > signs to compare these pairs of fractions.
I can compare fractions with the same denominator.
1.
3.
5.
2.
4.
6.
¾
�
�
⅓
�
�
¼
�
�
⅔
�
�
7.
9.
11.
13.
8.
10.
12.
14.
⅜
⅞
9 10
1 12
�
3 10
2 11
11 12
⅝
⅛
7 10
5 12
�
1 10
4 11
7 12
15.
17.
19.
16.
18.
20.
5 11
5 14
7 20
4 13
2 15
4 25
8 11
3 14
9 20
6 13
1 15
6 25
Name: ________________________
Fractions 1 Draw a line between the fraction and the correct shape.
7
9
3
4
1
6
5
9
7
8
7
10
3
8
4
5
Name: ________________________
Fractions 2
Work out the fractions of the shapes that are shaded.
4
3
8
4
8
Name: ________________________
Fractions 3
Work out fractions that are the same.
Is the same as
2
8
1
4
Is the same as
3
2
Is the same as
6
2
Is the same as
Real Life Fractions 1
1. A pizza has been divided into 8 equal slices. Harry eats a quarter of the pizza, and Arthur eats half of the pizza, how many slices are left?
2. Baket the Egyptian embalmer had 16 slaves to mummify.
Unfortunately he only managed to mummify a quarter of them before the rest rotted. How many slaves were preserved?
3. Pokemon cards are on special offer, they normally cost £1.50 per
packet but have been reduced to half price. How much will a packet cost now?
4. If ¼ of a packet of Jelly Babies is 7 sweets, how many are there in a
whole packet? 5. If Sally has ½ of a chocolate bar, and Sam has a ¼ of the same
chocolate bar, who has the most chocolate, Sally or Sam? 6. Paul had 60p, but he spent 40p. What fraction of his money did he
spend? 7. A large chocolate cake weighs 800g.How much does half of the cake
weigh? 8. How much does ¾ of the chocolate cake weigh?
Real Life Fractions 2
1. There are 38 Smarties in a packet. If I gave you half a packet how many Smarties would I have to give?
2. An Egyptian scribe wrote 100 papyrus documents, but 10 were ruined by a hungry camel. What fraction of the documents did the scribe lose?
3. I spent 84p at a bring and buy sale, and also gave three quarters of that amount to the Millennium Appeal. How much did I give to the Millennium Appeal?
4. Sixteen Martians visit Earth. Twelve of them are green. What fraction are green?
5. What fraction are not green?
6. In 4H there are 20 girls and 10 boys. What fraction of the class are girls?
7. If I have 1/2 of a cake and you have 2/4 of a cake, how much is there left?
8. There are 400 slaves working on the Pharaohs pyramid. 2/8 of the slaves are unable to work due to hunger today. How many slaves are working?
Real Life Fractions 1 Answers 1. 2 slices
2. 4 slaves
3. 75p
4. 28 Jelly babies
5. Sally
6. 2/3
7. 400g
8. 600g
Real Life Fractions 2 Answers 1. 19 smarties
2. 1/10 of documents
3. 63p
4. ¾ green
5. ¼ not green
6. 2/3 girls
7. none
8. 300
Equivalent Fractions
When two fractions are equivalent, this means they are the same in terms of shape and size, but are expressed using different numbers.
For example, these fractions are exactly the same, but because the larger shape is split into a different number of segments in each case, the fraction is expressed in a different way:
In Primary 5, children move onto finding equivalent fractions without the use of diagrams. At this stage, they would learn that whatever the numerator is multiplied by the denominator must also be multiplied by the same number, for example:
You can find out more about equivalent fractions using the link below:
Equivalent FractionsThese fractions are equivalent. The rectangles are the same. The amount shaded is equivalent.
Write the shaded fraction for each rectangle. Cut each section out. Match the rectangles with the equivalent amount shaded and stick each equivalent set together in your book.
6
12
3
4
1
12 6
5 10 8
4 18 3
4 9 10
=
Equivalent FractionsThese fractions are equivalent. The rectangles are the same. The amount shaded is equivalent.
Shade the second shape to be equivalent to the first and write the equivalent fractions.
41 =
=
=
=
8
3 6
10
=
12
3
4
1=
Equivalent FractionsThese fractions are equivalent. The rectangles are the same. The amount shaded is equivalent.
Write the fraction of each shape that is shaded and draw a line to match each equivalent fraction.
