(1) We can rewrite the original expression as:gbb wrote:What is the value of 10^(x+1) * 7^(y-1)?
(i) 10^x * 7^y = 2401
(ii) x+y =4
answer A
10^x * 10^1 * 7^y * 7^-1
which we can rearrange (and simplify) as:
10^x * 7^y * 10 * 1/7
Substituting in 10^x * 7^y = 2401, we get:
2401 * 10 * 1/7, which is just a bunch of numbers (and therefore solvable)... sufficient.
(2) we can pick an infinite number of different values for x and y which satisfy this equation. Different numbers will give us a different solution to the original question: insufficient.
(1) is sufficient, (2) isn't: choose (A).
