The G.P. is a1,2a2,22a3,…,29a10 with common ratio 21.
So 2n−1an=a1⋅(21)n−1, giving an=a1⋅(2)n−1.
n=1∑10an=a1⋅2−1(2)10−1=a1⋅2−131=31a1(2+1).
Setting this equal to 62: a1=2+12=2(2−1).
JEE Main 2026 — Mathematics Algebra
Let a1,2a2,22a3,…,29a10 be a G.P. of common ratio 21. If a1+a2+…+a10=62, then a1 is equal to :
Held on 21 Jan 2026 · Verified 6 Jul 2026.
2−2
2(2−2)
2−1
2(2−1)
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