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Question

How many terms of the AP 4, 11, 18, ______ will make the sum 795?

This question was previously asked in
HTET 2025 Level 1 PRT Question Paper (5-Jul-2026)
The correct answer is

15

For the AP 4, 11, 18, ..., the first term a = 4 and the common difference d = 11 - 4 = 7.

Sum of n terms, Sn = n/2 [2a + (n-1)d]. Setting Sn = 795 gives n/2 [8 + 7(n-1)] = 795.

This simplifies to n(7n + 1) = 1590, that is 7n^2 + n - 1590 = 0.

Solving this quadratic equation, n = (-1 + sqrt(1 + 44520))/14 = (-1 + 211)/14 = 210/14 = 15.

So 15 terms of the AP make the sum 795.

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Important Questions from Arithmetic Progression

  1. If the arithmetic mean of a, b, c is \(\rm \frac M 3\) and  \(\rm \frac{1}{a} + \frac{1}{b} = -\frac{1}{c} \) , then the arithmetic mean of a 2, b 2, c 2 is

  2. How many two-digit numbers are divisible by 3 ?

  3. A person saves Rs. 1000 more than he did the previous year. If he saves Rs. 2000 in the first year, in how many years will he save Rs. 170000?

  4. A car starts with a speed of 60 km/h with its speed increasing every one hour by 5 km/h. In how many hours will it cover 435 kms?

  5. How many natural numbers lie between 3 and 200 which are divisible by 7?

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