a certain meter records voltage

[urooj.khan]

a certain meter records voltage between 0 and 10 volts, inclusive. if the average value of 3 recordings from the meter was 8 volts, what was the smallest possible recording in volts?

A) 2
B) 3
C) 4
D) 5
E) 6

[stock.mojo11]

a certain meter records voltage between 0 and 10 volts, inclusive. if the average value of 3 recordings from the meter was 8 volts, what was the smallest possible recording in volts?

A) 2
B) 3
C) 4
D) 5
E) 6

(v1+v2+v3)/3=8

v1+v2+v3=24

For any one to be min, the other two must be max.

max for v =10, If v1 is min and v2,v3 are max

v1= 24-20=4

[RonPurewal]

the solution above is good.

what's more important than this particular solution, as usual, is the TAKEAWAY that you can get from it.

TAKEAWAY:

when you have numbers with a fixed sum or product:

if you want to MINIMIZE A QUANTITY, then you must MAXIMIZE ALL OTHER QUANTITIES in the sum or product.

if you want to MAXIMIZE A QUANTITY, then you must MINIMIZE ALL OTHER QUANTITIES in the sum or product.

if you make this realization, then this problem is simple:
you're trying to minimize one voltage reading.
this means that you should maximize the other readings: make two of them 10 volts each.
the third reading is thus 24 - 10 - 10, or 4 volts.