NCERT Solutions for Class 7th Maths Chapter 3 In-text Questions — A Tenth Part
Book page 51 Updated on2026-09-19
Q1.
The lengths of the body parts of a honeybee are given. Find its total length. Head: 2 3/10 units, Thorax: 5 4/10 units, Abdomen: 7 5/10 units
Page 51 — a honeybee, with its head, thorax and abdomen marked. Schematic drawing.
Answer
Add the three lengths.
Units: 2 + 5 + 7 = 14 Tenths: 3 + 4 + 5 = 12 12 tenths = 1 unit and 2 tenths Total = 14 + 1 units and 2 tenths = 15 2⁄10 units
In tenths:
23⁄10 + 54⁄10 + 75⁄10 = 152⁄10 = 15 2⁄10 units
Why it happens: 152 tenths = 150 tenths + 2 tenths = 15 units + 2 tenths, because every 10 tenths make one whole unit.
Q2.
The length of Shylaja’s hand is 12 4/10 units, and her palm is 6 7/10 units, as shown in the picture. What is the length of the longest (middle) finger?
Page 51 — the outer rectangle spans the whole hand, from fingertip to wrist; the inner one spans only the palm. Redrawn sketch.
Answer
Finger = hand – palm.
(12 + 4⁄10) – (6 + 7⁄10) We cannot take 7 tenths from 4 tenths, so split one unit from 12: 12 4⁄10 = 11 units and 14 tenths 14 tenths – 7 tenths = 7 tenths 11 units – 6 units = 5 units = 5 7⁄10 units
Doing it entirely in tenths:
124⁄10 – 67⁄10 = 57⁄10 = 5 7⁄10 units
Why it happens: borrowing here is the same as borrowing in whole numbers. One unit is worth 10 tenths, so 12 units and 4 tenths can be re-read as 11 units and 14 tenths without changing the value.
Q3.
Discuss what is being done here and why.
Answer
The two columns show the same subtraction 12 4⁄10 – 6 7⁄10, before and after regrouping.
In the left column, the tenths line reads 4 – 7. Since 4 tenths is not enough, the subtraction cannot start.
So one unit is taken from 12 and changed into 10 tenths. Now 12 units 4 tenths is rewritten as 11 units 14 tenths — the number has not changed, only the way it is split.
In the right column the tenths now read 14 – 7 = 7, and the units read 11 – 6 = 5, giving 5 7⁄10.
Why it happens: we always subtract starting from the smallest place value. When the top digit there is too small, we exchange one of the next bigger unit for ten of the smaller — exactly the "borrowing" used for 124 – 67 in whole numbers.
Check it yourself: add back — 5 7⁄10 + 6 7⁄10 = 11 14⁄10 = 12 4⁄10. The answer checks out.