Math (can you provide me with the working and ans?
posted by Mark .
A rectangular tank 28cm long and 18cm wide was filled with water to a dept of 7cm. When 12 marbles were added the level rose to 12cm. Find the average volume of the 12 marbles.

Math (can you provide me with the working and ans? 
Reiny
The Change in volume
= (28)(18)(5) cm^3
= 2520 cm^3
This was caused by the 12 marbles
that volume was 12(4/3)πr^3
= 16πr^3
16πr^3 = 2520
r^3 = 2520/(16π)
r = (2520/(16π))^(1/3)
I got appr 1.69 cm
Avg volume = (4/3)π(1.69)^3
= appr 20.22 cm^3
check my arithmetic
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