Question
Average of 20 numbers is 90. Average of first 8 numbers
is 125 while average of last nine numbers is 40. If ninth number is 25% less than the tenth number which is equal to the eleventh numbers then find the tenth number.Solution
Sum of ninth, tenth and eleventh number = 20 × 90 – 8 × 125 – 9 × 40 = 440 Let tenth number = x = eleventh number So, ninth number = 0.75 × x = 0.75x So, x + 0.75x + x = 440 Or, 2.75x = 440 Or, x = 160
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