1. The sum of the coefficients in the expansion of (3x − 2)5 is
- A−1
- B243
- C3125
- D1
Show answer
Answer: D. Put x = 1: the sum of the coefficients is (3 − 2)5 = 1. Adding 3 and 2 instead gives 55 = 3125.
By Team Megalecture · Updated 4 Nov 2026
23 exam-style questions on Maths · Sequences, series and the binomial theorem, each with the answer and a short explanation. Ten of them are below to try. The chapter test draws ten fresh questions each time and is marked the moment you finish, with your score by topic.
23 questions · 2 topics · 10 per test
Try each one, then open the answer. These ten stay the same; the test draws new ones every time.
Answer: D. Put x = 1: the sum of the coefficients is (3 − 2)5 = 1. Adding 3 and 2 instead gives 55 = 3125.
Answer: A. Multiply through by (x − 1)2(x + 2) and put x = 1: 1 = 3B, so B = 1/3. (The other constants are A = −1/9 and C = 1/9.)
Answer: C. ∛65 = 4(1 + 1/64)1/3 ≈ 4(1 + 1/192) = 4 + 1/48 ≈ 4.021. Leaving out the power 1/3 gives 4 + 4/64 ≈ 4.063, and not multiplying the 1/192 by 4 gives 4 + 1/192 ≈ 4.005.
Answer: A. d = Tn+1 − Tn = −3. Check: T1 = 4, T2 = 1, T3 = −2; 4 is the first term, not the difference.
Answer: A. H = 2ab/(a + b) = 2(1/10)/(7/10) = 2/7. 7/20 is the arithmetic mean and 1/√10 the geometric mean.
Answer: C. The term is 8C5(−x)5 = −56x5, since 8C5 = 56 and an odd power of −x is negative.
Answer: C. T10 = S10 − S9 = 320 − 261 = 59. 320 is the sum of the first ten terms, not the tenth term.
Answer: B. a/(1 − r) = 4 and a2/(1 − r2) = 16/3. Dividing the second by the first gives a/(1 + r) = 4/3; with a = 4(1 − r) this gives r = 1/2 and a = 2.
Answer: B. 1/3, G1, G2, G3, 27 are in G.P. with r4 = 81, so the means are 1, 3, 9 (or −1, 3, −9). Either way the product is 27; 9 is only the middle mean.
Answer: D. ar5 ÷ ar2 = r3 = 96/12 = 8, so r = 2 and a = 12/r2 = 3. Using ar3 for the 3rd term gives 1.5, and 2 is the common ratio, not the first term.
23, each with the answer and a short explanation, across 2 topics: Sequences and series, Binomial theorem and partial fractions. Every chapter test draws ten of them, so you can take it many times.
Yes. The test, the answers and the explanations are free and need no sign-up. Sign in only if you want your scores kept across devices.
The moment you press Finish: your score, the right answer and an explanation for every question, and the ones you got wrong saved in My mistakes to retry.
Yes. In practice mode and on your results you can switch the explanations to Urdu.
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