On a certain nonstop trip, Marta averaged x miles per hour for 2 hours and y miles per hour for the remaining 3 hours. What was her average speed, in miles per hour, for the entire trip?
(1) 2x + 3y = 280
(2) y = x + 10
A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D. EACH statement ALONE is sufficient.
E. Statements (1) and (2) TOGETHER are NOT sufficient.
the answer is ( A )
Sp = is the avg speed
x = is the first speed
y = is the second speed
T1= 2 hours
T2= 3 hours
Distance = D1 + D2
D1 = x*2
D2 = y*3
Total time = 5
Sp = total Distance/ total Time
SP = (D1 + D2) / 5
Sp = (x * 2 + y * 3)/5
now (I) is suffieicent because it give us the nominator
(II) is not sufficent because it give us 2 variable that can not be inserted in our equation
so the answer is A