Ananya observes that the square of a number ending in 9, like $1 9^{2} = 361$ or $2 9^{2} = 841$ , always ends in 1.
What is the units digit of $7 9^{2}$ ?

Question

Ananya observes that the square of a number ending in 9, like 19^2 = 361 or 29^2 = 841, always ends in 1. What is the units digit of 79^2?

Accepted Answer

1. 9^2 = 81 ends in 1, so any number ending in 9 has a square ending in 1. 79^2 = 6241, units digit 1.

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