Answer:
n = 7.
Step-by-step explanation:
Sum S of an AP = (n/2)[2a + d(n - 1)]
112 = (n/2)[2*25 - 3(n -1)]
n/2 (53 - 3n) = 112
n(53 - 3n) = 224
-3n^2 + 53n - 224 = 0
3n^2 - 53n + 224 = 0
(3n - 32 )(n - 7 ) = 0
n = 7, 32/3
So n must be 7 as its a whole number.
