If c +d = 11 and c and d are positive integers, which of the following is a possible value for 5c +8d?
(A) 55
(8) 61
(C) 69
(D) 83
(E) 88
(A) 55
(8) 61
(C) 69
(D) 83
(E) 88
5c + 8d = 5(c + d) + 3d = 55 + 3d
subtract 55 from each answer and see if it gives a multiple of 3 = 3d
if it does, calculate the value of d, it should be in the range:
dmin = 1 (d is a positive integer)
dmax = 10 (c is at least 1)
only the answer 61 works.
