Practice

Question 1

5 x 81

Answer 1

First halve it
40.5

Then multiply by 10
405

Question 2

5 x 37

Answer 2

First halve it
18.5

Then multiply by 10
185

Question 3

81 / 5

Answer 3

First double it
162

Then divide by 10
16.2

Question 4

What’s 18% of 140?

Answer 4

Well 20% is 28

And actually for 2% you just move the decimal left
So 2% is 2.8

So 28-2.8
25.2

Question 5

Percentage trick is start with 100% and use 50%, 10% 5% and 1%

Quick way to do 5% or 1%?

Answer 5

Just move decimal to the left from 50% and 10% respectively

Question 6

5%=

Answer 6

5/100 or 1/20

Question 7

2/11=

Answer 7

Well 1/11 is 9.09% so 2/11 is 18.18%

Question 8

X is 10% of Y

Answer 8

X = 10/100 *Y

Question 9

X is 33.3% more/less than Y

Answer 9

X = (1 +1/3)Y
X=(1 -1/3)Y

X=4/3Y
X=2/3Y
Or
Y=3/2X

Question 10

X is 40% of Y

Answer 10

X=2/5Y

Question 11

840 / 4

Answer 11

Remember to divide by four you can halve it and then halve it again

So half is 420
Half again is 210

Question 12

729 / 8

Answer 12

That becomes 720/8 + 9/8
90 + 9/8

Remember 9/8 is just 8/8 + 1/8 so 1 and 1/8
1/8 is 0.125

So
91.125!

Question 13

21/4

Answer 13

Example or simplifying to 20/4 + 1/4 !

Question 14

Quick way of doing 25%

Answer 14

Halve it (50%) then halve it again!

Equivalent to doing 1/4

Question 15

6+2

Answer 15

8

Question 16

7+2

Answer 16

9

Question 17

Quick way to do 5/8?

Answer 17

4/8 plus 1/8!

So 50% plus 12.5%

Question 18

10/4

Answer 18

Another way of thinking about it is

4/4+4/4+2/4

Question 19

5/4

Answer 19

Another way of thinking about it is
4/4 and 1/4

So 1.25

Question 20

75% discount?

Answer 20

That just means real price is 25%

Question 21

Way to do 25%?

Answer 21

Divide by two then divide by two again

Question 22

Way to do 75%?

Answer 22

Determine 25% (half then half again) then subtract