the average of 10 numbers is 60 . out of 10 numbers the average of first 6 no . is 68 , and last 6 numbers is 75 then find 7 th number ?
"7 th number = sum of 1 st 6 no . s + sum of last 6 no . s - sum of 11 no . s answer = 6 * 68 + 6 * 75 - 10 * 60 = 258 answer is c"
subtract(add(multiply(6, 68), multiply(6, 75)), multiply(10, 60))