If $2 n=14$, the value of $10 n$ is
(A) 14
(B) 140
(C) 70
(D) 28
(E) 56
Solution 1

If $2 n=14$, then $n=\frac{14}{2}=7$.

When $n=7$, the value of $10 n$ is $10 \times 7=70$.

Solution 2

Multiplying both sides of the given equation by 5 , we get $5 \times 2 n=5 \times 14$, and so $10 n=70$.

ANSWER: (C)