parulmahajan89 wrote:if a equals sum of even integers from 2-20 inclusive and b is sum of odd integers from 1-19,inclusive. What is value of a-b?
1) 1
2) 10
3) 19
4) 20
5) 21
Alternate approach:
For any set of evenly spaced integers:
average = median = (biggest + smallest)/2.
sum = (number)(average).
a = the sum of the EVEN integers between 1 and 20, inclusive:
number of integers = 10.
average = median = (biggest + smallest)/2 = (20+2)/2 = 11.
sum = (number)(average) = 10*11 = 110.
b = the sum of the ODD integers between 1 and 20, inclusive:
number of integers = 10.
average = median = (biggest + smallest)/2 = (19+1)/2 = 10.
sum = (number)(average) = 10*10 = 100.
Thus:
a-b = 110-100 = 10.
The correct answer is
B.
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