Question 6: Let the m-th and n-th terms of a Geometric progression be 3/4 and 12, respectively, when m < n. If the common ratio of the progression is an integer r, then the smallest possible value of r + n – m is
Answer:
B.
3 /4 12
mth nth
m > n
Given r is an integer, So rk = 12/(3/4) = 16
rk = 24 or 42
Since asked for minimum possible value, Taking rk = {(-2)}^2 or {(-4)}^2
k = n – m (From m how many terms we have to jump to reach n)
We have two cases r = – 2 and n – m = 4 —-> r + n – m = 2
r = – 4 and n – m = 2 —-> r + n – m = – 2
-2 is the smallest possible value
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