The average weight of 10 sacks of wheat is decreased by 1 lb when 2 of them 26 and 30 lbs are replaced by 2 rice sacks. What was the average weight of the two rice sacks?
- 21 lbs
- 22 lbs
- 23 lbs
- 24 lbs
- 25 lbs
The Usual Method
Let the average weight of 2 rice sacks be ‘x’ lbs.
Hence total weight of two rice sacks = 2x lbs.
This is substituted for two wheat sacks of 26 and 30 lbs. i.e 26 + 30 =56 lbs.
Since the average weight of 10 sacks of wheat is decreased by 1 lb, reduction in total weight = 1 x 10 = 10 lbs.
Estimated Time to arrive at the answer = 30 seconds.
Note that the reduction of 10 lbs in the total weight of 10 sacks is attributable to the two rice sacks. Hence, each rice sack should have 5 lbs less weight than the average weight of the two wheat sacks of 26 and 30 lbs.
Average of 26 and 30 = lbs
Hence average weight of a sac of rice =28 – 5 = 23 lbs.
Estimated Time to arrive at the answer = 10 seconds.