A student made this factor tree.
What is √1764?
Leaves: 2, 2, 3, 3, 7, 7 → three pairs
Take one from each pair: 2 × 3 × 7
= 42
Trap: 21 drops the pair of 2s.
Answer: 42
Square Roots & Cube Roots · Exercise 6 of 6
30 diagram-based Square Root and Cube Root questions in the style of current bank, SSC, railway and campus placement papers. Every question has its own figure to read: factor trees, square plots and cubes, ladder and diagonal triangles, number lines, unit-digit and long-division tables, Venn diagrams of squares and cubes, infinite-radical trees, number machines, given-value tables and area models.
A student made this factor tree.
What is √1764?
Leaves: 2, 2, 3, 3, 7, 7 → three pairs
Take one from each pair: 2 × 3 × 7
= 42
Trap: 21 drops the pair of 2s.
Answer: 42
Here is a factor tree of 9261.
What is the cube root of 9261?
Leaves: 3, 3, 3 and 7, 7, 7 → two groups of three
Take one from each group: 3 × 7
= 21
Trap: 63 takes 3 × 3 × 7.
Answer: 21
The factor tree of 2450 is shown.
By what least number must 2450 be multiplied to make a perfect square?
2450 = 2 × 5² × 7²
Only the 2 has no partner
Multiply by 2: 4900 = 70²
Trap: 5 and 7 are already paired.
Answer: 2
The factor tree of 8640 is shown.
By what least number must 8640 be divided so that the quotient is a perfect cube?
8640 = 2⁶ × 3³ × 5
2⁶ and 3³ are already in groups of three
Remove the lone 5: 8640 ÷ 5 = 1728 = 12³
Trap: 15 also removes a 3 and breaks the 3³ group.
Answer: 5
A square garden has the area shown.
How many metres of fencing are needed to go once around it?
Side = √2,025 = 45 m
Perimeter = 4 × 45
= 180 m
Trap: 45 is one side only.
Answer: 180
Three square plots have the areas shown in the chart.
What is the total length of fencing needed to go around all three plots?
Sides: √576 = 24, √784 = 28, √1,089 = 33
Sum of sides = 85
Fencing = 4 × 85 = 340 m
Trap: 85 adds the sides without multiplying by 4.
Answer: 340
A ladder leans against a vertical wall.
How high up the wall does the ladder reach?
Height² = 13² − 5²
= 169 − 25 = 144
Height = 12 m
Trap: 8 m subtracts the lengths, not their squares.
Answer: 12 m
Instead of walking along two edges of a rectangular field, Neha walks straight across it.
How many metres does she save?
Along the edges: 30 + 40 = 70 m
Diagonal = √(30² + 40²) = √2,500 = 50 m
Saving = 70 − 50 = 20 m
Trap: 50 is the diagonal, not the saving.
Answer: 20
Two poles 9 m and 4 m tall stand 12 m apart on level ground. A wire joins their tops. The triangle below shows the part of the picture above the shorter pole.
How long is the wire?
Upright side = difference in heights = 5 m
Wire = √(12² + 5²) = √169
= 13 m
Trap: 15 m uses the full 9 m height.
Answer: 13 m
A solid cube has the volume shown.
What is the length of each edge?
Edge = ∛2,744
2,744 ends in 4 → root ends in 4; 2 lies between 1³ and 2³ → 1
Edge = 14 cm
Trap: 52.4 is close to √2,744, a square root.
Answer: 14 cm
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