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ICSE Question Bank
2019Q8(a)Arithmetic Progression
NumericalModerate3 marks

The sum of the first three terms of an Arithmetic Progression (A.P.) is 42 and the product of the first and third term is 52. Find the first term and the common difference.

Topic: Arithmetic progression

Previous-year question practice database

Answer

Solution diagram
Solution diagram
Exam answer

d = 12, or –12

Explanation

Let the terms be a – d, a, a + d ∴ a – d + a + a – d = 42 3a = 42 ∴ a = 14 (a – d)(a + d) = 52 – d2 = 52 d2 = 196 – 52 d2 = 144 ∴d = ±12 d = 12, or –12

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