All Exams Test series for 1 year @ ₹349 only
Question

What is the sum of the squares of the numbers from 3 to 18?

This question was previously asked in
RRB NTPC 2019 CBT 1 Question Paper (8-Mar-2021) (Shift 2)
The correct answer is
2104

Sum of Squares Calculation

This problem requires calculating the sum of squares for a specific range of numbers (3 to 18). We can use the standard formula for the sum of the squares of the first n natural numbers and adapt it for the given range.

Sum of Squares Formula

The formula for the sum of the squares of the first n natural numbers is:

\sum_{i=1}^{n} i^2 = \frac{n(n+1)(2n+1)}{6}

Applying the Formula

To find the sum of squares from 3 to 18 ($\sum_{n=3}^{18} n^2$), we first calculate the sum of squares from 1 to 18 and then subtract the sum of squares from 1 to 2 ($\sum_{n=1}^{2} n^2$).

Step 1: Calculate Sum of Squares from 1 to 18

Using the formula with n = 18:

\sum_{i=1}^{18} i^2 = \frac{18(18+1)(2 \times 18 + 1)}{6}

= \frac{18 \times 19 \times (36 + 1)}{6}

= \frac{18 \times 19 \times 37}{6}

= 3 \times 19 \times 37

= 57 \times 37

= 2109

Step 2: Calculate Sum of Squares from 1 to 2

Using the formula with n = 2:

\sum_{i=1}^{2} i^2 = \frac{2(2+1)(2 \times 2 + 1)}{6}

= \frac{2 \times 3 \times (4 + 1)}{6}

= \frac{2 \times 3 \times 5}{6}

= \frac{30}{6}

= 5

Step 3: Calculate the Final Sum

Subtract the sum of squares from 1 to 2 from the sum of squares from 1 to 18:

\sum_{n=3}^{18} n^2 = \sum_{i=1}^{18} i^2 - \sum_{i=1}^{2} i^2

= 2109 - 5

= 2104

Conclusion

The sum of the squares of the numbers from 3 to 18 is 2104.

Was this answer helpful?

Similar Questions

  1. Fifteen houses are located in a row such that the distance between two adjacent houses is equal. If the distance between the $1^{\text{st}}$ and $15^{\text{th}}$ house is 560 ft., then what is the distance between the $3^{\text{rd}}$ and $7^{\text{th}}$ house?
  2. The sum of the first 20 terms of the series $\frac{1}{5 \times 6} + \frac{1}{6 \times 7} + \frac{1}{7 \times 8} + \dots$ is:

Important Questions from Sequence & Series

  1. 4 is related to 64 following a certain logic. Following the same logic, 9 is related to 729. To which of the following is 12 related following the same logic?
    (NOTE: Operations should be performed on whole numbers without breaking down the numbers into their constituent digits. E.g., 13 – Operations on 13 such as adding/multiplying, etc., to 13 can be performed. Breaking down 13 into 1 and 3 and then performing mathematical operations on 1 and 3 is not allowed.)

  2. What should come in place of ? in the given series based on the English alphabetical order?

    ACE, FHJ, KMO, PRT, ?

  3. Which of the following numbers will replace the question mark (?) in the given series? 

    3, 17, 83, 329, ?, 1961

  4. Two sets of numbers are given below. In each set of numbers, certain mathematical operation(s) on the first number result(s) in the second number. Similarly, certain mathematical operation(s) on the second number result(s) in the third number and so on. Which of the given options follows the same set of operations as in the given sets? (NOTE: Operations should be performed on the whole numbers, without breaking down the numbers into their constituent digits. E.g. 13 – Operations on 13 such as adding/subtracting/multiplying to 13 can be performed. Breaking down 13 into 1 and 3 and then performing mathematical operations on 1 and 3 is not allowed.)

  5. Find the area (in cm²) of the sector, where the radius of the circle is 24 cm and length of the arc is 7 cm.

Need Expert Advice?
Upcoming Exams
RRB ALP
July 28, 2026
RRB Group D
August 03, 2026
Test Series
RRB NTPC img
Railways
RRB NTPC Under Graduate 2026 New Mock Test Series
1459 Tests 2 Tests Free
216 Attempts
4.3(512)
English, Hindi, Telugu +7 More

Start Your Preparation with Prepp Mobile App

Download the app from Google Play & App Store
Download the app from Google Play & App Store
Prepp Mobile App