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25 December 2015

Short Mathematics Tricks

Squaring
In this simple trick we need to modify the equation and make the units digit zero. After all it is easy to multiply when units digit is zero.
For example - Find square of 43
= (43+3) × (43-3) + (3×3)
=(46×40) + 9
= (460×4) + 9
= 1840 + 9 = 1849

Multiplication with 5
Simply multiply the number by 10 and then divide it by 2.
For example 99×5= 990/2= 495
Multiplication with 99

Multiply the number with 100 and then minus same number from the result. Let's take an example
Multiply 32×99 = 3200 - 32 = 3168

Square root
Best method to find square root of large numbers is by dividing the number into parts. Let's take an example
Find square √ 1936
√ 1936 = √ 4 × √ 484 = √ 4 × √ 4 × √ 121 = 2×2×11 = 44

Time and Work
Every question in in time and work chapter can be solved easily by finding efficiency of workers or subject (such as pipes).

For example - A takes 10 days to complete a job. B takes 20 days to complete the same job. In how many days they will complete the job if they work together ?
A's efficiency = 100/10 = 10% per day
B's efficiency = 100/20 = 5% per days
A and B can do 15% of the work in a day if they work together. So they can do the whole job in 100/15 = 6.66 days or 6 days and 18 hours.

Estimation
That's the most important technique. This is not a secret that every successful candidate is using this technique during exams.

Example - 112 × 92
Simply 112 × 9 = 1008
Add a zero 10080 and then add 224 to 10080.
Answer is 10304

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