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NCERT Solutions for Class 5th Maths Chapter 1 Question 1 — Let Us Do

Book page 5 Updated on2026-09-19

Q1.
1. Fill in the blanks by continuing the pattern in each of the following sequences. Discuss the patterns in class. (a)
456567678
Sequence (a) as printed on page 5 — three numbers are given and four boxes are empty.
Answer

Step 1 — find the jump. Take one number away from the next one.

567 – 456 = 111
678 – 567 = 111
So the rule is: add 111 each time.

Step 2 — keep adding 111.

678 + 111 = 789
789 + 111 = 900
900 + 111 = 1,011
1,011 + 111 = 1,122

The full chain:

456 → 567 → 678 → 789 → 900 → 1,011 → 1,122
Discuss in class: The first four numbers look like a staircase — 456, 567, 678, 789. Each digit goes up by 1. But the pattern of digits breaks at 900, because 789 + 111 needs carrying. The rule add 111 never breaks, only the pretty look of the digits does.
Q2.
1. (b) 1,050 → __ → 3,150 → 4,200 → __ → __ → __
Answer

Step 1 — find the jump. Use two numbers that are next to each other.

4,200 – 3,150 = 1,050
So the rule is: add 1,050 each time.

Step 2 — fill the gap in the middle.

1,050 + 1,050 = 2,100
Check: 2,100 + 1,050 = 3,150 ✓

Step 3 — carry on to the end.

4,200 + 1,050 = 5,250
5,250 + 1,050 = 6,300
6,300 + 1,050 = 7,350
1,050 → 2,100 → 3,150 → 4,200 → 5,250 → 6,300 → 7,350
Tip: These are the numbers you get by counting in 1,050s — 1 × 1,050, 2 × 1,050, 3 × 1,050 and so on. The seventh one is 7 × 1,050 = 7,350 ✓
Q3.
1. (c) 5,501 → 6,401 → 7,301 → __ → __ → __ → __
Answer

Step 1 — find the jump.

6,401 – 5,501 = 900
7,301 – 6,401 = 900
Rule: add 900 each time.

Step 2 — keep adding 900.

7,301 + 900 = 8,201
8,201 + 900 = 9,101
9,101 + 900 = 10,001
10,001 + 900 = 10,901
5,501 → 6,401 → 7,301 → 8,201 → 9,101 → 10,001 → 10,901
Discuss in class: Watch what happens at 9,101 + 900. The hundreds are 1 + 9 = 10 hundreds, which is a whole thousand. That thousand joins the 9 thousands to make 10 thousands — and a 5-digit number appears: 10,001.
Q4.
1. (d) 10,100 → 10,200 → 10,300 → __ → __ → __ → __ ↓ __ ← 10,900 ← __
Answer

Step 1 — find the jump.

10,200 – 10,100 = 100 → rule: add 100 each time.

Step 2 — finish the top row (it runs left to right).

10,300 + 100 = 10,400
10,400 + 100 = 10,500
10,500 + 100 = 10,600
10,600 + 100 = 10,700

Step 3 — the arrow turns down, then the bottom row runs right to left.

10,700 + 100 = 10,800 (bottom row, right box)
10,800 + 100 = 10,900 (already printed ✓)
10,900 + 100 = 11,000 (bottom row, left box)

The full chain: 10,100 · 10,200 · 10,300 · 10,400 · 10,500 · 10,600 · 10,700 · 10,800 · 10,900 · 11,000

Check it yourself: The printed 10,900 lands exactly where our counting says it should. That is a good sign the rule is right.
Q5.
1. (e) 10,105 → 10,125 → __ → __ → __ → __ → __ ↓ __ ← __ ← __
Answer

Step 1 — find the jump.

10,125 – 10,105 = 20 → rule: add 20 each time.

Step 2 — top row, left to right.

10,125 + 20 = 10,145
10,145 + 20 = 10,165
10,165 + 20 = 10,185
10,185 + 20 = 10,205
10,205 + 20 = 10,225

Step 3 — down, then bottom row right to left.

10,225 + 20 = 10,245
10,245 + 20 = 10,265
10,265 + 20 = 10,285

The full chain: 10,105 · 10,125 · 10,145 · 10,165 · 10,185 · 10,205 · 10,225 · 10,245 · 10,265 · 10,285

Discuss in class: Every number in this chain ends in 5. That is because we started at a number ending in 5 and kept adding 20 — and 20 never changes the ones digit.
Q6.
1. (f) 10,992 → 10,993 → __ → __ → __ → __ → __ ↓ __ ← __ ← __
Answer

Step 1 — find the jump.

10,993 – 10,992 = 1 → rule: add 1 each time.

Step 2 — just count on.

10,994 · 10,995 · 10,996 · 10,997 · 10,998 · 10,999 · 11,000 · 11,001

The full chain: 10,992 · 10,993 · 10,994 · 10,995 · 10,996 · 10,997 · 10,998 · 10,999 · 11,000 · 11,001

Discuss in class: The interesting box is the one after 10,999. Nine hundreds, nine tens and nine ones are all full. Adding one more makes them all roll over to 0 and pushes 1 into the thousands: 10,999 + 1 = 11,000. This is exactly like an odometer in a bus turning over.
Q7.
1. (g) 10,794 → 10,796 → 10,798 → __ → __ → __ → __ ↓ __ ← __ ← __
Answer

Step 1 — find the jump.

10,796 – 10,794 = 2
10,798 – 10,796 = 2 → rule: add 2 each time.

Step 2 — keep adding 2.

10,798 + 2 = 10,800
10,800 + 2 = 10,802
10,802 + 2 = 10,804
10,804 + 2 = 10,806
10,806 + 2 = 10,808
10,808 + 2 = 10,810
10,810 + 2 = 10,812

The full chain: 10,794 · 10,796 · 10,798 · 10,800 · 10,802 · 10,804 · 10,806 · 10,808 · 10,810 · 10,812

Tip: Every number here is even, because we started at an even number and kept adding 2.
Q8.
1. (h) 73,005 → 72,004 → __ → __ → __ → __ → __ ↓ __ ← __ ← __
Answer

This chain goes down, not up.

Step 1 — find the jump.

73,005 – 72,004 = 1,001 → rule: take away 1,001 each time.

Step 2 — keep subtracting 1,001. An easy way: take away 1,000, then take away 1 more.

72,004 – 1,001 = 71,003
71,003 – 1,001 = 70,002
70,002 – 1,001 = 69,001
69,001 – 1,001 = 68,000
68,000 – 1,001 = 66,999
66,999 – 1,001 = 65,998
65,998 – 1,001 = 64,997
64,997 – 1,001 = 63,996

The full chain: 73,005 · 72,004 · 71,003 · 70,002 · 69,001 · 68,000 · 66,999 · 65,998 · 64,997 · 63,996

Discuss in class: Look at 68,000 – 1,001. There are no ones and no thousands to take from, so we have to borrow — and the answer jumps to 66,999, not 67,999. Many children make this slip. Always take away 1,000 first, then the extra 1.
Q9.
1. (i) 82,350 → 83,350 → __ → __ → __ → __ → __ ↓ __ ← __ ← __
Answer

Step 1 — find the jump.

83,350 – 82,350 = 1,000 → rule: add 1,000 each time.

Step 2 — keep adding 1,000. Only the thousands digit changes.

84,350 · 85,350 · 86,350 · 87,350 · 88,350 · 89,350 · 90,350 · 91,350

The full chain: 82,350 · 83,350 · 84,350 · 85,350 · 86,350 · 87,350 · 88,350 · 89,350 · 90,350 · 91,350

Discuss in class: Notice 89,350 + 1,000. Nine thousands plus one more thousand makes ten thousands, which carries into the ten-thousands place: 8 becomes 9 and the thousands digit becomes 0 → 90,350.
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