alleryFind the average of $5, 10, 15, 20$ and $25$.
- $12$
- $14$
- $15$
- $17$
Show answer and solution
Correct answer: C. $15$
Sum $= 5+10+15+20+25 = 75$.
Average $= \dfrac{75}{5} = 15$.
AFCAT Averages — practice questions
Explore 4 free Averages questions in AFCAT Quantitative Reasoning. Open each question or exercise to read its content, reference answers and available explanation.
Practise Averages with Quill →Averages questions and exercises with answers
Showing questions 1–4 of 4.
Find the average of $5, 10, 15, 20$ and $25$.Read the answer and worked solution →What is the average of the first five natural numbers?Read the answer and worked solution →The average of $11$ numbers is $50$. If the average of the first six is $49$ and that of the last six is $52$, find the sixth number.Read the answer and worked solution →The average weight of A, B and C is $45$ kg. The average of A and B is $40$ kg, and the average of B and C is $43$ kg. Find B's weight.Read the answer and worked solution →
Worked practice questions
What is the average of the first five natural numbers?
- $2$
- $2.5$
- $3$
- $3.5$
Show answer and solution
Correct answer: C. $3$
Sum $= 1+2+3+4+5 = 15$.
Average $= \dfrac{15}{5} = 3$.
The average of $11$ numbers is $50$. If the average of the first six is $49$ and that of the last six is $52$, find the sixth number.
- $52$
- $54$
- $56$
- $58$
Show answer and solution
Correct answer: C. $56$
**Set up.** Total of all $11$ numbers $= 11 \times 50 = 550$. Sum of first six $= 6 \times 49 = 294$. Sum of last six $= 6 \times 52 = 312$.
**Key observation.** The sixth number is counted in both groups (it's the last of the first six *and* the first of the last six). So $294 + 312 = 606 = \text{sum of all 11} + \text{sixth number}$.
**Solve.** Sixth number $= 606 - 550 = 56$.
**Why option A (52) is tempting.** Picking the average of the second group directly ignores the overlap
the sixth number is *systematically pulled toward whichever group has the higher mean* relative to the overall mean.
How to practise
- Choose a Averages question and try to work out your answer.
- Open the question to check the correct answer and read its worked solution.
- Continue in the app for bite-sized lessons, explanations and review with Quill. You can start without creating an account.
Put it into practice
Continue with Averages practice for AFCAT. Read explanations as you go. No signup form needed to start.
Practise Averages →