Maths Olympiad Prep

Track / Stage 2 / 23 of 240 #263 of 2444

Problem 263

Number theory Difficulty 2.2 Multiple choice CEMC Pascal · Canada · 2014

If 2×2×3×3×5×6=5×6×n×n2 \times 2 \times 3 \times 3 \times 5 \times 6 = 5\times 6 \times n \times n, then nn could equal

Pick one

Next problem →

Official solution

Solution 1

We rewrite the left side of the given equation as 5×6×(2×3)×(2×3)5 \times 6 \times (2 \times 3) \times (2 \times 3).

Since 5×6×(2×3)×(2×3)=5×6×n×n5 \times 6 \times (2 \times 3) \times (2 \times 3) = 5 \times 6 \times n \times n, then a possible value of nn is 2×32 \times 3 or 6.

Solution 2

Since 2×2×3×3×5×6=5×6×n×n2 \times 2 \times 3 \times 3 \times 5 \times 6 = 5 \times 6 \times n \times n, then 1080=30n21080 = 30n^2 or n2=36n^2 = 36.

Thus, a possible value of nn is 6. (The second possible value for nn is 6-6.)

Solution 3

Dividing both sides by 5×65 \times 6, we obtain 2×2×3×3=n×n2 \times 2 \times 3 \times 3 = n \times n, which is equivalent to n2=36n^2 = 36.

Thus, a possible value of nn is 6. (The second possible value for nn is 6-6.)

Source: CEMC, University of Waterloo, licensed CC-BY-NC-4.0. Statement reproduced verbatim; metadata (topic, difficulty, ordering) added by this project.