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NCERT Solutions for Class 4th Maths Chapter 9 Observe the pattern and complete the answers — In-text Questions

Book page 143 Updated on2026-09-19

Q1.
Observe the pattern and complete the answers.
1 × 3 = ______2 × 3 = ______4 × 3 = ______
10 × 3 = ______20 × 3 = ______40 × 3 = ______
100 × 3 = ______200 × 3 = ______400 × 3 = ______
Answer
1 × 3 = 32 × 3 = 64 × 3 = 12
10 × 3 = 3020 × 3 = 6040 × 3 = 120
100 × 3 = 300200 × 3 = 600400 × 3 = 1200

Each column keeps the group size 3 and makes the number of groups ten times bigger.

1 × 3 = 3, so 10 × 3 = 30 and 100 × 3 = 300
2 × 3 = 6, so 20 × 3 = 60 and 200 × 3 = 600
4 × 3 = 12, so 40 × 3 = 120 and 400 × 3 = 1200
Why it happens: Ten times as many groups gives ten times as much, and that just adds a 0 at the end.
Q2.
Observe the pattern and complete the answers.
2 × 4 = ______4 × 2 = ______8 × 1 = ______
20 × 4 = ______40 × 2 = ______80 × 1 = ______
200 × 4 = ______400 × 2 = ______800 × 1 = ______
Answer
2 × 4 = 84 × 2 = 88 × 1 = 8
20 × 4 = 8040 × 2 = 8080 × 1 = 80
200 × 4 = 800400 × 2 = 800800 × 1 = 800

All three columns give the same answers.

All three columns end with the same numbers — 8, 80 and 800.

Why it happens: 2 groups of 4, 4 groups of 2 and 8 groups of 1 are all 8 things. Making the number of groups ten or a hundred times bigger keeps them equal.
Q3.
Observe the pattern and complete the answers.
3 × 4 = ______3 × 5 = ______3 × 9 = ______
30 × 4 = ______30 × 5 = ______30 × 9 = ______
300 × 4 = ______300 × 5 = ______300 × 9 = ______
Answer
3 × 4 = 123 × 5 = 153 × 9 = 27
30 × 4 = 12030 × 5 = 15030 × 9 = 270
300 × 4 = 1200300 × 5 = 1500300 × 9 = 2700

Here the number of groups stays 3, 30, 300 and the group size changes.

3 × 9 = 27
30 × 9 = ten times 27 = 270
300 × 9 = hundred times 27 = 2700
Tip: Learn the small fact well. The big ones are then just the same digits with zeros behind them.
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