The average of eleven numbers is 54. The average of the first four numbers is 48 and that of the next four numbers is 25% more than the average of the first four. The ninth number is 8 greater than the 11thnumber and the tenth number is 4 greater than the 11% number. What is the average of the 9th and the 10thnumbers?
Show answer & explanation
Correct answer: B
Explanation
Correct answer is option 2 i.e. 56
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Concept |
Understanding |
Application |
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Average = (Sum of numbers)/(Total numbers) |
Average of 11 numbers = 54 Average of first four numbers = 48 Average of Next four numbers is 25% more than first four numbers |
Sum of 11 numbers = 54 × 11 = 594 Sum of first four numbers = 48 × 4 = 192 Average of next four numbers = 48× 1.25 = 60 Sum of next four numbers = 60×4 = 240 So, total sum of first eight numbers =192+240 = 432
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The 9th number is 8 greater than the 11th number and the 10th number is 4 greater than the 11th number
Let 11th number is ‘x’ then, 9th number and 10th number will be (x + 8) and (x + 4) respectively |
Sum of 9th , 10th and 11th number =594-432= 162 x+x+8+x+4 = 162 x = 50 9th number =x+8 =50+8 = 58 10th number = x+4 = 50+4 = 54 Average = (58+54)/2 = 56 |