The least number of squares to be added in the figure to make AB a line of symmetry is
Figure Q.10 — squares about the line AB
Options:
(A) 6
(B) 4
(C) 5
(D) 7
Official Answer Key:
A
Step-by-Step Solution & Explanation
For AB to be a line of symmetry, every square must have a mirror partner reflected across AB.
Step 1 — inventory. Taking AB as the axis, with rows counted outward from it:
Above AB: 1 square (in the first row above).
Below AB: 5 squares — three in the first row below and two in the second row below.
Step 2 — supply the missing mirrors.
Each of the 5 squares below requires a mirror image above. None of them currently has one, because the single existing square above does not sit in a mirrored column. ⇒ 5 squares to be added above.
The 1 existing square above likewise has no partner below. ⇒ 1 square to be added below.
Step 3 — total: 5 + 1 = 6 squares
SECTION 1: ENGINEERING MATHEMATICS
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