The first term of an AP is 4 and the sum of the first three terms is 18. Find the product of the first three terms
292
272
192
172
Correct answer is C
Using the sum of an AP, S\(_n\) = \(\fra{n}{2}\) [ 2a + (n - 1)d]
S\(_3\) = \(\fra{3}{2}\) [ 2a + (3 - 1)d]
18 = \(\fra{3}{2}\) [ 2a + 2d]
2a + 2d = 12
a = 4
2(4) + 2d = 18 --> 8 + 2d = 12
2d = 4; d = 2
a = 4: a + d
= 4 + 2 = 6
a + 2d = 4 + 2]2]
= 8
product of the terms = 4 * 6 * 8 = 192