q: If X is the sum of first 100 positive even integers and Y is the sum of first 100 positive odd integers, what is the value of x-y?
Please try to explain your answers
Options:
(A) 0
(B) 25
(C) 50
(D) 75
(E) 100
a: First even minus first odd = 2-1 = 1;
The sum of first 2 even integers minus the sum of first 2 odd integers = (2+4)-(1+3) = 2;
The sum of first 3 even integers minus the sum of first 3 odd integers = (2+4+6)-(1+3+5) = 3;
We can see the patterns here, so the sum of first 100 positive even integers minus the sum of first 100 positive odd integers will be 100. The answer is (E).
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q: Which of the following numbers is divisible by each one of 3, 7, 9 and 11 ?
Options:
(A) 2079
(B) 456
(C) 974
(D) 562
(E) 300
a: 639 is not divisible by 7
2079 is divisible by each of 3, 7, 9, 11. The answer is (A).
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q: A train running at the speed of 60 km/hr crosses a pole in 9 seconds. Find the length of the train?
Options:
(A) 150
(B) 8827
(C) 166
(D) 199
(E) 121
a: Speed = 60*(5/18) m/sec = 50/3 m/sec
Length of Train (Distance) = Speed * Time
(50/3) * 9 = 150 meter The answer is (A).
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q: Look at this series: 53, 53, 39, 39, 25, 25, ... What number should come next?
Options:
(A) A) 12
(B) B) 11
(C) C) 27
(D) D) 53
(E) E) 86
a:
In this series, each number is repeated, then 14 is subtracted to arrive at the next number. The answer is (B).
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