NCERT Solutions Ganita Prakash (Part 1) Chapter 3 Figure it Out — Addition and Subtraction of Decimals

Book page 75 Updated on2026-09-05

Q1.

Find the sums (a) 5.3 + 2.6 (b) 18 + 8.8 (c) 2.15 + 5.26 (d) 9.01 + 9.10 (e) 29.19 + 9.91 (f) 0.934 + 0.6 (g) 0.75 + 0.03 (h) 6.236 + 0.487

Answer

Line up the decimal points, filling short numbers with zeros on the right.

	Set up	Carrying	Answer
(a)	5.3 + 2.6	no carry	7.9
(b)	18.0 + 8.8	no carry in tenths, carry 1 in ones	26.8
(c)	2.15 + 5.26	no carry	7.41
(d)	9.01 + 9.10	carry 1 in ones	18.11
(e)	29.19 + 9.91	carry in hundredths, tenths and ones	39.10
(f)	0.934 + 0.600	carry 1 into the units	1.534
(g)	0.75 + 0.03	no carry	0.78
(h)	6.236 + 0.487	carry in thousandths and hundredths	6.723

Sample (e): 29.19 + 9.91
Hundredths: 9 + 1 = 10 → write 0, carry 1
Tenths: 1 + 9 + 1 = 11 → write 1, carry 1
Ones: 9 + 9 + 1 = 19 → write 9, carry 1
Tens: 2 + 1 = 3
= 39.10

Why it happens: writing 18 as 18.0 and 0.6 as 0.600 does not change their values, but it keeps every digit in its correct column. Misaligned decimal points are the commonest mistake in this exercise.

Q2.

Find the differences (a) 5.6 – 2.3 (b) 18 – 8.8 (c) 10.4 – 4.5 (d) 17 – 16.198 (e) 17 – 0.05 (f) 34.505 – 18.1 (g) 9.9 – 9.09 (h) 6.236 – 0.487

Answer

	Set up	Borrowing	Answer
(a)	5.6 – 2.3	none	3.3
(b)	18.0 – 8.8	borrow 1 unit as 10 tenths	9.2
(c)	10.4 – 4.5	borrow 1 unit as 10 tenths	5.9
(d)	17.000 – 16.198	borrow right across	0.802
(e)	17.00 – 0.05	borrow 1 unit as 100 hundredths	16.95
(f)	34.505 – 18.100	borrow 1 ten	16.405
(g)	9.90 – 9.09	borrow 1 tenth as 10 hundredths	0.81
(h)	6.236 – 0.487	borrow in thousandths and hundredths	5.749

Sample (d): 17.000 – 16.198
17.000 = 16 units + 9 tenths + 9 hundredths + 10 thousandths
Thousandths: 10 – 8 = 2
Hundredths: 9 – 9 = 0
Tenths: 9 – 1 = 8
Units: 16 – 16 = 0
= 0.802

Why it happens: in (d) and (e) the top number has no decimal digits at all, so we write it as 17.000 or 17.00 first. Then a single unit is opened into 1000 (or 100) of the smallest parts, and the subtraction proceeds normally.

Check it yourself: add each answer back to the number that was subtracted. For (h): 5.749 + 0.487 = 6.236 ✓

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