Question

He average of 10 reading is 25.5. In this, the average of the first three is 20 and the next four is 26. If the eight reading is 5 less than the night one and also 8 less than the tenth one, then find the eight reading?

Answer 1

Answer:

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Step-by-step explanation:

Let x1 , x2 , x3 , ... , x9 , x10 representing every time he reads

From the first sentence : x1 + x2 + x3 + ... + x10 = 25.5 * 10      ##1

Second one : x1 + x2 + x3 = 20 * 3      ##2

Third one : x4 + x5 + x6 + x7 = 26 * 4      ##3

Fourth one : x8 = x9 - 5 = x10 - 8      ##4

Using ##2 and ##3 in ##1

(20 * 3) + (26 * 4) + x8 + x9 + x10 = 25.5 * 10     ##5

From ##4

x9 = x8 + 5 and x10 = x8 + 8     ##6

Using ##6 in ##5

60 + 104 + (3 * x8) + 13 = 255

3 * x8 =78

x8 = 26 Ans