The average of 8 numbers is 7.5. If one of them is deleted, the average of the remaining 7 numbers becomes 8.5. What is the deleted number?
Correct answer: D. 0.5
- A. 0.2
- B. 0.3
- C. 0.4
- D. 0.5
Explanation
If the eight numbers are a, b, c, d, e, f, g, h. Following equation can be formed (a+b+c+d+e+f+g+h)/8= 7.5 ---- (1) If h is deleted, the equation becomes (a+b+c+d+e+f+g)/7=8.5 (a+b+c+d+e+f+g)= 8.5×7= 59.5 Putting this value in equation (1) ((a+b+c+d+e+f+g) +h)/8= 7.5 (59.5+h)/8=7.5 59.5+h=7.5×8 59.5+h=60 h=60-59.5 h=0.5
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