Question
Download Solution PDFThe average of 30 numbers is 12. The average of the first 20 of them is 11 and that of the next 9 is 10. The last number is:
Answer (Detailed Solution Below)
Detailed Solution
Download Solution PDFGiven:
Average of 30 numbers = 12
Average of the first 20 numbers = 11
Average of the next 9 numbers = 10
Formula Used:
Total sum = Average × Number of terms
Calculation:
Sum of all 30 numbers = 12 × 30
⇒ Sum of all 30 numbers = 360
Sum of the first 20 numbers = 11 × 20
⇒ Sum of the first 20 numbers = 220
Sum of the next 9 numbers = 10 × 9
⇒ Sum of the next 9 numbers = 90
Sum of the last number = Total sum - (Sum of the first 20 numbers + Sum of the next 9 numbers)
⇒ Sum of the last number = 360 - (220 + 90)
⇒ Sum of the last number = 360 - 310
⇒ Sum of the last number = 50
The last number is 50.
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