Bunuel
In a store, 40 items are arranged on a rack in 5 rows and 8 columns. The average (arithmetic mean) of the price of items in each row (m) is \(X_m\) [1 ≤ m ≤5]. The average of the price of items in each column (n) is \(Y_n\) [1 ≤ n ≤ 8]. What is the average price of all items on the rack?
(1) \(X_1 + X_2 + ... + X_5 = $850\)
(2) \(Y_1 + Y_2 + ... + Y_8 = $1,360\)
Experts' Global Explanation:Average prices of items in row1, row2, row3, row4, and row 5 are X
1, X
2, X
3, X
4, and X
5 respectively.
Average prices of items in column1, column2.......column7, and column8 are Y
1, Y
2.......Y
7, and Y
8 respectively.
The total number of items = 40.
The average price of all items = (Sum of the prices of all items)/(Total number of items).
We need to find whether the value of “Sum of the prices of all items / 40” can be determined.Statement (1)Since X
1 represents the average price of items in row1, it follows that 8X
1 must be the sum of the prices for the 8 items in row1.
Similarly, for row2 through row5, the values 8X
2,8X
3,8X
4, and 8X
5 respectively must be the sum of prices for the items in their corresponding rows.
The average price of all items
= Sum of the prices of all items/40
= (Sum of price of items in row1 + Sum of price of items in row2 + ....... + Sum of price of items in row5) / 40
= (8X
1 + 8X
2 + ....... + 8X
5) / 40
= 8(X
1 + X
2 + ....... + X
5) / 40
= 8(850) / 40
It is possible to determine with certainty the average price of all items on the rack.
Hence, Statement (1) is sufficient.Statement (2)Since Y
1 represents the average price of items in column1, it follows that 5Y
1 must be the sum of the prices for the 5 items in column1.
Similarly, for column2 through column8, the values 5Y
2,5Y
3 ......5Y
7, and 5Y
8 respectively must be the sum of prices for the items in their corresponding columns.
The average price of all items
= Sum of the prices of all items/40
= (Sum of price of items in column1 + Sum of price of items in column2 + ....... + Sum of price of items in column8) / 40
= (5Y
1 + 5Y
2 + ....... + 5Y
8) / 40
= 5(Y
1 + Y
2 + ....... + Y
8) / 40
= 5(1360)/40
It is possible to determine with certainty the average price of all items on the rack.
Hence, Statement (2) is sufficient.D is the correct answer choice.