Three of the following four number groups are alike in a certain way. Choose the one that does not belong to the group.
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → (625, 25, 5)
Compare the first two numbers with the cube and the square of the third number.
Option (1) (1000, 100, 10) — \( 10^3 = 1000 \) and \( 10^2 = 100 \): (cube, square, number).
Option (2) (512, 64, 8) — \( 8^3 = 512 \) and \( 8^2 = 64 \): (cube, square, number).
Option (3) (625, 25, 5) — \( 5^2 = 25 \), but \( 5^3 = 125 \), not 625; 625 is \( 5^4 \).
Option (4) (216, 36, 6) — \( 6^3 = 216 \) and \( 6^2 = 36 \): (cube, square, number).
In three groups the first number is the cube of the third; 625 is not the cube of 5, so (625, 25, 5) is the odd one out.