Arithmetic Progression Sum

CAT 2025 Slot 3 · Quantitative Ability · Easy · Algebra

This is an easy Quantitative Ability question from the CAT 2025 Slot 3 paper. It tests Algebra. The full answer key and a step-by-step explanation are below — try it yourself first, then reveal the solution.

In an arithmetic progression, if the sum of fourth, seventh and tenth terms is 99, and the sum of the first fourteen terms is 497, then the sum of first five terms is

Answer

65

Explanation

Let first term be aa and common difference be dd. T4+T7+T10=(a+3d)+(a+6d)+(a+9d)=3a+18d=99    a+6d=33T_4 + T_7 + T_{10} = (a+3d) + (a+6d) + (a+9d) = 3a + 18d = 99 \implies a + 6d = 33. S14=142(2a+13d)=7(2a+13d)=497    2a+13d=71S_{14} = \frac{14}{2}(2a + 13d) = 7(2a + 13d) = 497 \implies 2a + 13d = 71. Solving these equations: From a=336da = 33 - 6d, substitute into second: 2(336d)+13d=71    66+d=71    d=52(33 - 6d) + 13d = 71 \implies 66 + d = 71 \implies d = 5. Then a=3330=3a = 33 - 30 = 3. Sum of first 5 terms S5=3+8+13+18+23=65S_5 = 3 + 8 + 13 + 18 + 23 = 65.

Related Algebra questions

Practise this under exam conditions

Sign in to solve it with a live timer, the on-screen CAT calculator, and streak and accuracy tracking across every question you attempt.

Solve in the workspace