(a) The 6th term of an A.P is 35 and the 13th term is 77.
MATHEMATICS
WAEC 1997
(a) The 6th term of an A.P is 35 and the 13th term is 77. Find the 20th term.
(b).jpg)
The Venn diagram represents three subsets P, Q and R of the universal set U. Copy the Venn diagram. Shade and indicate the regions represented by (i) \(P \cap Q' \cap R\) ; (ii) \(P' \cap Q \cap R'\).
Explanation
(a) \(T_{n} = a + (n - 1)d\) (terms of an A.P)
\(T_{6} = a + 5d = 35 ... (1)\)
\(T_{13} = a + 12d = 77 ... (2)\)
(2) - (1) : \(7d = 42 \implies d = 6\)
\(a + 5(6) = 35 \implies a + 30 = 35\)
\(a = 5\)
\(\therefore T_{20} = a + 19d = 5 + 19(6)\)
= \(5 + 114 = 119\)
(b).jpg)
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