Hi Everyone,

Although GMAT doesn't test your ability to perform complicated calculations, it would be beneficial to know some calculation tricks that would save you some time.

Trick 7: Rapidly Square Any Number Ending in 5Multiply the tens digit by the next whole number then affix the number 25

\(65^2: 6*7=42 ==> 'affix' 25 ==> 4225\)

Trick 8: Rapidly Multiply Any Two-Digit Number by 11Write the number leaving some space between the two digits, then insert the sum of the number's two digit in between.

24*11 ==> 2

? 4 ==> 2+4=6 ==> 264

Trick 9: Rapidly Multiply by 25 (or 0.25, 2.5, 250, etc.)Divide the number by 4 and affix or insert Zeroes or decimal points

Example: 28*25 ==> 28/4 = 7 ==> 700 (add 2 Zeroes)

Trick 10: Rapidly Divide by 25 (or 0.25, 2.5, 250, etc.)Remove Zeroes or decimal points then multiply the number by 4

Example: 700/25 ==> 7/25 ==> 7*4=28

Trick 24: Rapidly Square Any Two-Digit Number ending in 1\(21^2

==> 20^2=400

==> Add: 20+21=41

==> Add: 400+41= 441

==> 21^2 = 441\)

Trick 59: Rapidly Multiply Any Three-Digit Number by 11 (advanced variation of trick 8)

Write the number leaving some space between the two digits, then insert the summations of the numbers in between (summations of 2 digits everytime; as shown below).

Example:

342*11=??

34

2*11=

3--

2 (write the first & the last number "3"& "2")

3

42*11=3-

62 (the sum of 4+2)

342*11=3

762 (the sum of 3+4)

Source: Rapid Math Tricks & Tips. EDWARD H. JULIUS

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