WAEC - Further Mathematics (2024 - No. 5)
If the n\(^{th}\) term of a linear sequence (A.P) is (5n - 2), find the sum of the first 12 terms of the sequence.
120
183
366
732
Açıklama
n\(^{th}\) = (5n - 2)
1st term = 5 - 2 = 3
2nd term = 10 - 2 = 8
3rd term = 15 - 2 = 13
Hence, common difference, d = 5
S\(_n\) = \(\frac{n}{2}\)[2a + (n - 1)d]
S\(_{12}\) = \(\frac{12}{2}\)[2 x 3 + (12 - 1)5]
= 6[6 + 11 x 5] = 6[6 + 55] = 6 x 61 = 366.