Kerala PSC - Maths Shortcut Tricks (Multiplication) - 4

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In our previous tutorial we have learnt shortcut for multiplying teens with teens without using a pen or pencil or even writing on paper. In this tutorial we will try to learn how to multiply any humber with teens (x X 12, 13...19).

Shortcut Method for Multiplication
x X Teens
Let Multiply

2132 x 12 = ?

Prefix a Zero before the given number. In R.H.S. number (i.e. 12) ignore 1 and multiply by 2, If 13 then, if 16 then 6 and so on. Lets solve the above given problem.

Here start from right and move to left
Step 1 : 2 x 2 = 4
Step 2 : 3 x 2 + 2 = 8
Step 3 : 2 x 1 + 3 = 5
Step 4 : 2 x 2 + 1 = 5
Step 5 : 2 x 0 + 2 = 2
Every time after accomplishing multiplication add the previous number, until you reach the last Number.

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Try one more Example

4356 x 13 = ?

Step 1 : 6 x 3 = 18 (Drop 8 carry 1)
Step 2 : 5 x 3 = 15 + 6 + Carry 1 = 22 (Drop 2 carry 2)
Step 3 : 3 x 3 = 9 + 5 + Carry 2 = 16 (Drop 6 carry 1)
Step 4 : 4 x 3 = 12 + 3 + Carry 1 = 16 (Drop 6 carry 1)
Step 5 : 0 x 3 = 0 + 4 + Carry 1 = 5

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Example : 3

4628 x 15 = ?

Step 1 : 5 x 8 = 40 (Drop 0 carry 4)
Step 2 : 5 x 2 = 10 + 8 + Carry 4 = 22 (Drop 2 carry 2)
Step 3 : 5 x 6 = 30 + 2 + Carry 2 = 34 (Drop 4 carry 3)
Step 4 : 5 x 4 = 20 + 6 + Carry 3 = 29 (Drop 9 carry 2)
Step 5 : 5 x 0 = 0 + 4 + Carry 2 = 6