The average of twelve numbers is 45 5 The averageof the first four numbers is 41 5 and that of the n...........

Quantitative Aptitude (CGL) Average

The average of twelve numbers is 45.5. The averageof the first four numbers is 41.5 and that of the next five numbers is 48. The

10^thnumberis 4 more than the 11^thnumber and 9 more than the 12^thnumber. Whatis the average of the 10^thand 12^th

numbers?

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SSC CGL 4th March 2020 Shift-1

47.8

46.6

- The average of 12 numbers is 45.5, so their sum is 12 × 45.5 = 546.

- The average of the first 4 numbers is 41.5, so their sum is 4 × 41.5 = 166.

- The average of the next 5 numbers (5th to 9th) is 48, so their sum is 5 × 48 = 240.

- The sum of the last three numbers (10th, 11th, and 12th) is 546 - (166 + 240) = 140.

- Let 10th = x, 11th = y, 12th = z.

- x = y + 4, x = z + 9 ? y = x - 4, z = x - 9.

- x + y + z = 140

So, x + (x - 4) + (x - 9) = 140 ? 3x - 13 = 140 ? 3x = 153 ? x = 51.

- 12th number z = x - 9 = 51 - 9 = 42.

- The average of 10th and 12th = (51 + 42) / 2 = 93 / 2 = 46.5.

So, none of the options match exactly, but the closest is option 4, 46.6.

- Option 4: 46.6 is the best of the choices given.

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