Some teachers use diagrams like the following, depicting a:b = c:d, or a/b = c/d, to help their students visualize proportions. 0 a b 0 d (a) If a = 5 when b=25, determine c when d = 100. (b) If b=2400 when a = 256, determine d when c = 1024. (c) If b=22.5 when a = 1.1, determine d when c = 4.2. (a) If a = 5 when b=25, determine c when d = 100. c=