This question has been answered by atleast three experts in two diff threads. Don't know where it is appropiate one to air my doubts so I have continued in the recent thread. Most of them have analysed the problem and its nuances rather than solving it algeberically. I find that it difficult to conceive the problem so minutely when the time available is under 2 mins. Is it better to solve it rather brutishly by simultaneous eq. in the above problem
the number are either 7 or 77 so there are certain nos of 7 and 77 say x and y respectively
7x+77y = 350 or
x + 11 y = 50 ( eq 1) this is similar to the approach in post of lunarpower.
x + y = n (eq 2) n is the no of terms in the series. subtracting 2 from 1
10y = 50-n of the options A. 38 B. 39 C. 40 D. 41 E. 42
only n = 40 will result in y being an integer.
