The average of five positive numbers is 308. The average of first two numbers is 482.5 and the average of last two numbers is 258.5. What is the third number?
Let the numbers be $$A_1 , A_2 , A_3 , A_4 , A_5$$
=> $$A_1 + A_2 + A_3 + A_4 + A_5 = 308 * 5 = 1540$$
Also, $$A_1 + A_2 = 482.5 * 2 = 965$$
and $$A_4 + A_5 = 258.5 * 2 = 517$$
=> $$A_3 = 1540 - 965 - 517 = 58$$
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