GMAT Practice Question: If m is an even integer, v is an odd integer, and m>v>0...
Question
If m is an even integer, v is an odd integer, and m>v>0, which of the following represents the number of even integers less than m and greater than v ?
- m-v/2-1
- m-v-1/2
- m-v/2
- m-v-1
- m-v
Topics: odds/evens, counting evenly spaced integers, translations
Solution
Step 1
We translate “m is an even integer” and “v is an odd integer” into expressions using integer parameters.
v = 2j + 1 m = 2k
Step 2
The even integers between v and m start at the first even after v and end at the last even before m.
first even = v + 1 = 2(j + 1) last even = m - 2 = 2(k - 1)
Step 3
We count the number of terms in this evenly spaced sequence with step 2.
2(k - 1) - 2(j + 1)/2 + 1 = (k - 1 - (j + 1)) + 1 = k - j - 2 + 1 = k - j - 1
Step 4
We substitute back k = m/2 and j = v - 1/2 into k - j - 1.
k - j - 1 = m/2 - v - 1/2 - 1
Step 5
We simplify the expression in terms of m and v.
= m - (v - 1)/2 - 1 = m - v + 1/2 - 1 = m - v - 1/2
Answer
m - v - 1/2
