Three numbers which are co-prime to each other are such that the product of the first two is 551 and that of the last two is 1073. The sum of the three numbers is________?
Correct answer: C. 85
- A. 75
- B. 81
- C. 85
- D. 89
Explanation
Since 551 = 19 x 29 and 1073 = 29 x 37, the common middle number is 29. Thus the three numbers are 19, 29 and 37, whose sum is 19 + 29 + 37 = 85. A common mistake is 81, usually caused by incorrect factorisation of 1073.
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