Out of 4 numbers, the average of first 3 is 19 and last
3 is 20. If the last number is 21. Find the first number?
A18Correct AnswerIncorrect Answer
B9Correct AnswerIncorrect Answer
C13Correct AnswerIncorrect Answer
D16Correct AnswerIncorrect Answer
Solution
Sum of first three numbers = 19 × 3 = 57 Given that last number is = 21 ∴ sum of all the four numbers = 57 + 21 = 78 ..(i) Sum of last 3 digits = 20 × 3 = 60..(ii) By subtracting (ii) from (i), we will get the first number, the first number, First number = (i) – (ii) = 78 – 60 = 18
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