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GeneralEducation
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GMAT Sample Questions and solution tips 09 Apr 2014, 04:37
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Concept tested: Even/Odd number
Question:If a is odd and b is even, is ab odd, or even?

Answer: xy is even
An odd number can be represented as 2n + 1, and an even number can be represented as 2n, where n is an integer.Multiplying 2n + 1 and 2n would yield 4n2 +2n, which is always even, since 2 is a factor of both terms.

Mantra: odd number times an even number is always even.
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GMAT Sample Questions and solution tips 10 Apr 2014, 04:01
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Concept tested: Exponents
Question: Calculate (-1)273

Answer: -1
–1 raised to any even power is 1 {eg (–1) × (–1) = 1}.
–1 raised to any odd power will equal –1 {eg (–1) × (–1) × (–1) = -1}.
Since, 273 is an odd number, so (-1)273= –1.

Mantra: (-1) raised to an even power is equal to 1 and (-1) raised to odd power is equal to +1
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GMAT Sample Questions and solution tips 11 Apr 2014, 03:22
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Concept tested: Exponents and roots
Question: ( 7√x)7 = ?

a) x49 b) x c) X1/7 d) 1


Answer: x

( 7√x)7 = ( x1/7) 7= x(1/7)* 7 = x

Mantra: n√x can be written as x1/n
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GMAT Sample Questions and solution tips 01 May 2014, 04:32
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Concept tested: Even/Odd numbers
Question: If x and y are both odd integers , what is x/y ?
a) Odd
b) Even
c) Can’t be determined

Answer: Can’t be determined

If x is divisible by y , then obviously then x/ y is an odd integer. But it is not given whether x is divisible by y or not. So, we can’t determine it with given information.

Mantra: Check whether outcome of a calculation is an integer or not , before deciding whether it can be even or odd.
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GMAT Sample Questions and solution tips 02 May 2014, 04:26
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Concept tested: Exponents
Question: If xy < 0 , then x is
a) < 0
b) >0
c) Can’t be determined

Answer: < 0

If xy < 0 , then irrespective of the value of y , x is also negative.

Case 1 : x=2 , y =3 xy = 23 = 8 > 0
Case 2: x= -2 , y =3 xy = (-2)3 = -8 < 0

Mantra: If xy < 0 , x is also negative but it is not true vice versa. i.e if x < 0, then not necessarily xy < 0
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GMAT Sample Questions and solution tips 03 May 2014, 02:50
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Concept tested: Unit Digit
Question: What is the units digit of (28)(34)(57)?
a) 3
b) 0
c) 5

Answer: 0

We need not multiply the entire numbers to find the unit digit. Multiplying 2 and 5 , we get 10 (unit digit ‘0’). Hence this number when multiplied by any nymber any number of times will yield ‘0’ as unit digit.


Mantra: When a number with ‘0’ in its unit digit is multiplied with any other number, unit digit will remain same i.e. ‘0’.
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GMAT Sample Questions and solution tips 06 May 2014, 06:09
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Concept tested: Factoring
Question: Simplify 5^3 + 5^4 + 5^3 + 5^4
a) 625
b) 1500
c) 2500

Answer: 1500

5^3 is common in all terms. Factoring out the common term,

5^3 + 5^4 + 5^3 + 5^4
= 5^3 ( 1 + 5 + 1 + 5 )
= 5^3 ( 12 )
=125 *12
= 1500
Mantra: Look out to find the common term and factor it out to simply calculations and save time.
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GMAT Sample Questions and solution tips 08 May 2014, 02:19
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nehasingh1020
Concept tested: Exponents
Question: If xy < 0 , then x is
a) < 0
b) >0
c) Can’t be determined

Answer: < 0

If xy < 0 , then irrespective of the value of y , x is also negative.

Case 1 : x=2 , y =3 xy = 23 = 8 > 0
Case 2: x= -2 , y =3 xy = (-2)3 = -8 < 0

Mantra: If xy < 0 , x is also negative but it is not true vice versa. i.e if x < 0, then not necessarily xy < 0



The answer should be can't be determined as either x can be negative or y can be negative in which case x is positive. Isnt it?
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Schools: Oxford'17 (WL) Insead July'17 (I) Judge'17 (D)
GMAT 1: 690 Q49 V34
Schools: Oxford'17 (WL) Insead July'17 (I) Judge'17 (D)
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GMAT Sample Questions and solution tips 17 Apr 2015, 17:09
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Quote:
Concept tested: Unit Digit
Question: What is the units digit of (28)(34)(57)?
a) 3
b) 0
c) 5

Answer: 0

We need not multiply the entire numbers to find the unit digit. Multiplying 2 and 5 , we get 10 (unit digit ‘0’). Hence this number when multiplied by any number any number of times will yield ‘0’ as unit digit.


Mantra: When a number with ‘0’ in its unit digit is multiplied with any other number, unit digit will remain same i.e. ‘0’.

that's incorrect
something wrong with picking up unit digits, you picked up 10th digits to show answer to unit digit, it should be
(28)(34)(57) = 8*4*7 == 32 * 7 == 32 * 7 = 4

Answer is 4

if you multiply (28)(34)(57) == 54254
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GMAT Sample Questions and solution tips 11 May 2017, 10:09
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