NCERT Solutions for Class 5th Maths Chapter 13 Find 5 common multiples of the following pairs of numbers. — Let Us Do (Question 1)
Book page 166 Updated on2026-09-19
Q1.
(a) 2 and 3
Answer
Five common multiples of 2 and 3 are 6, 12, 18, 24, 30.
Multiples of 2
2, 4, 6, 8, 10, 12 …
Multiples of 3
3, 6, 9, 12 …
Common multiples
6, 12, 18, 24, 30 …
Write the 2 times table.
Write the 3 times table under it.
Circle the numbers that appear in both. The smallest is 6.
Keep adding 6. 6 → 12 → 18 → 24 → 30
Why it happens: 2 and 3 share no factor except 1. When that happens, the first common multiple is simply the two numbers multiplied together: 2 × 3 = 6.
A note on the book: In this list your book prints the label (f) twice — once for "9 and 12" and again for "8 and 12". So there are nine pairs in all, even though the last label reads (h). We have answered all nine, in the order they are printed.
Q2.
(b) 5 and 8
Answer
Five common multiples of 5 and 8 are 40, 80, 120, 160, 200.
Multiples of 5
5, 10, 15, 20, 25, 30, 35, 40, 45 …
Multiples of 8
8, 16, 24, 32, 40, 48, 56, 64, 72 …
Common multiples
40, 80, 120, 160, 200 …
Write the 5 times table.
Write the 8 times table under it.
Circle the numbers that appear in both. The smallest is 40.
Keep adding 40. 40 → 80 → 120 → 160 → 200
Why it happens: 5 and 8 share no factor except 1. When that happens, the first common multiple is simply the two numbers multiplied together: 5 × 8 = 40.
Q3.
(c) 2 and 4
Answer
Five common multiples of 2 and 4 are 4, 8, 12, 16, 20.
Multiples of 2
2, 4, 6, 8 …
Multiples of 4
4, 8 …
Common multiples
4, 8, 12, 16, 20 …
Write the 2 times table.
Write the 4 times table under it.
Circle the numbers that appear in both. The smallest is 4.
Keep adding 4. 4 → 8 → 12 → 16 → 20
Why it happens: 4 is already a multiple of 2, so every multiple of 4 is also a multiple of 2. That is why the first common multiple is 4 itself — the bigger number.
Q4.
(d) 3 and 9
Answer
Five common multiples of 3 and 9 are 9, 18, 27, 36, 45.
Multiples of 3
3, 6, 9, 12, 15, 18 …
Multiples of 9
9, 18 …
Common multiples
9, 18, 27, 36, 45 …
Write the 3 times table.
Write the 9 times table under it.
Circle the numbers that appear in both. The smallest is 9.
Keep adding 9. 9 → 18 → 27 → 36 → 45
Why it happens: 9 is already a multiple of 3, so every multiple of 9 is also a multiple of 3. That is why the first common multiple is 9 itself — the bigger number.
Q5.
(e) 5 and 10
Answer
Five common multiples of 5 and 10 are 10, 20, 30, 40, 50.
Multiples of 5
5, 10, 15, 20 …
Multiples of 10
10, 20 …
Common multiples
10, 20, 30, 40, 50 …
Write the 5 times table.
Write the 10 times table under it.
Circle the numbers that appear in both. The smallest is 10.
Keep adding 10. 10 → 20 → 30 → 40 → 50
Why it happens: 10 is already a multiple of 5, so every multiple of 10 is also a multiple of 5. That is why the first common multiple is 10 itself — the bigger number.
Q6.
(f) 9 and 12
Answer
Five common multiples of 9 and 12 are 36, 72, 108, 144, 180.
Multiples of 9
9, 18, 27, 36, 45, 54, 63, 72 …
Multiples of 12
12, 24, 36, 48, 60, 72 …
Common multiples
36, 72, 108, 144, 180 …
Write the 9 times table.
Write the 12 times table under it.
Circle the numbers that appear in both. The smallest is 36.
Keep adding 36. 36 → 72 → 108 → 144 → 180
Why it happens: 9 and 12 share the factor 3. So their first common multiple is not 9 × 12 = 108, but the smaller number 36. After that you add 36 each time.
Q7.
(f) 8 and 12
Answer
Five common multiples of 8 and 12 are 24, 48, 72, 96, 120.
Multiples of 8
8, 16, 24, 32, 40, 48 …
Multiples of 12
12, 24, 36, 48 …
Common multiples
24, 48, 72, 96, 120 …
Write the 8 times table.
Write the 12 times table under it.
Circle the numbers that appear in both. The smallest is 24.
Keep adding 24. 24 → 48 → 72 → 96 → 120
Why it happens: 8 and 12 share the factor 4. So their first common multiple is not 8 × 12 = 96, but the smaller number 24. After that you add 24 each time.
Q8.
(g) 6 and 8
Answer
Five common multiples of 6 and 8 are 24, 48, 72, 96, 120.
Multiples of 6
6, 12, 18, 24, 30, 36, 42, 48 …
Multiples of 8
8, 16, 24, 32, 40, 48 …
Common multiples
24, 48, 72, 96, 120 …
Write the 6 times table.
Write the 8 times table under it.
Circle the numbers that appear in both. The smallest is 24.
Keep adding 24. 24 → 48 → 72 → 96 → 120
Why it happens: 6 and 8 share the factor 2. So their first common multiple is not 6 × 8 = 48, but the smaller number 24. After that you add 24 each time.
Q9.
(h) 6 and 9
Answer
Five common multiples of 6 and 9 are 18, 36, 54, 72, 90.
Multiples of 6
6, 12, 18, 24, 30, 36 …
Multiples of 9
9, 18, 27, 36 …
Common multiples
18, 36, 54, 72, 90 …
Write the 6 times table.
Write the 9 times table under it.
Circle the numbers that appear in both. The smallest is 18.
Keep adding 18. 18 → 36 → 54 → 72 → 90
Why it happens: 6 and 9 share the factor 3. So their first common multiple is not 6 × 9 = 54, but the smaller number 18. After that you add 18 each time.
Q10.
What do you notice about the common multiples of different pairs of numbers? Discuss in class.
Answer
Sample answer: Every pair of numbers has endless common multiples. The smallest one matters most — once you have it, all the others come from adding it again and again. And the smallest one follows a pattern, depending on how the two numbers are related.
Kind of pair
Examples from this exercise
First common multiple
One number is a multiple of the other
2 and 4, 3 and 9, 5 and 10
The bigger number itself — 4, 9, 10
The two share nothing except 1
2 and 3, 5 and 8
The two multiplied — 6, 40
The two share a factor bigger than 1
8 and 12, 6 and 8, 6 and 9, 9 and 12
Smaller than the product — 24, 24, 18, 36
Three things to notice:
There is always a smallest common multiple, but never a biggest one. The list goes on for ever.
Every common multiple is a multiple of the smallest one. For 6 and 8 the list is 24, 48, 72, 96 — the 24 times table.
Common multiples are never smaller than the bigger of the two numbers.
Why it happens: A common multiple is a spot both animals can land on. Once they have met once, both patterns start again from that spot, so they will meet again after the same gap — over and over, for ever.