Free Tips to do Mental Math Questions Easy in 2011- Part 2

This is my second part of tips to solve math problems. Please find some tips to math questions easy. These tricks are easy to remember to do all match calculations

First Blog-Free Tips to do math Questions easy

9. How to multiply by 12?

First multiply the number by 10. To that product, add twice the number to reach the answer.

Example: 45 X 12

First Multiply: 45 x 10 = 450.

Then Multiply: 5 x 2 = 90.

Then Add 450 + 90 = 540

2^nd trick

As above, first multiply the number by 10. What you do then is add half of that product to the product to get the answer.

Example: – 32 X 15

First Multiply: 32 X 10 = 320.

Then Divide: 320 ÷ 2 = 160

Then Add: 320 + 160 = 480

11. How to multiply by 1.5, 2.5, 3, 5 etc.

This is made a lot easier if you first double the 1.5, 2.5 or other multiplier and then halve the other number, before multiplying the two products. (It's a lot easier when multiplying even numbers than odd numbers).

Example A:  – 3.5 X 16

First Double: 3.5 X 2 = 7.

Then Halve: 16 ÷ 2 = 8.

Then Multiply: 7 X 8 = 56

Example B. – 2.5 X 13

First Double: 2.5 X 2 = 5.

Then Halve: 13 ÷ 2 = 6.5.

Then Multiply: 5 X 6.5 = 32.5

12. How to divide by 1.5, 2.5, 3, 5 etc.

This technique is very similar to number 4. What you do hear is double both the divisor and the dividend, before dividing.

Example 1:. – 28 ÷ 3.5

First Double: 28 X 2 = 56.

Then Double: 3.5 X 2 = 7.

Then Divide: 56 ÷ 7 = 8

Example 2. – 17 ÷ 1.5

First Double: 17 X 2 = 34.

Then Double: 1.5 X 2 = 3.

Then Divide: 34 ÷ 3 = 11.333 (the answer). As you can see, the even numbers work a lot easier than the odds.

13. How to do percentages?

It is common knowledge that 'percent' literally means 'for every hundred'. However, this quick way to solve any percentage problem is not so widely known. All you do is multiply the two numbers and then move the decimal point two spaces left (divide by 100). Remember to ignore any decimal points and zeroes and re-affix them at the end.

Example: 10% of 20

First Multiply: 10 X 20 = 200

Then Move the decimal point two spaces left = 2.0

Also it’s useful to know that you can always spin percentages and arive at the same answer, e.g. 4% of 52 is the same as 52% of 4.