GMAT Sample Questions and solution tips

Question

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.

GeneralEducation · Answer

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

GeneralEducation · Answer

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

GeneralEducation · Answer

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.

GeneralEducation · Answer

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

GeneralEducation · Answer

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’.

GeneralEducation · Answer

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.

harishrakshan · Answer

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?

UJs · Answer

that's incorrect 
something wrong with picking up unit digits, you picked up 10th digits to show answer to unit digit, it should be 
(2  8  )(3  4  )(5  7  ) = 8*4*7 == 32 * 7 == 3  2   * 7 = 4

Answer is 4

if you multiply (28)(34)(57) == 5425  4

bumpbot · Answer

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