If an 11-digit number 5y5884805x6 is divisible by 72, then the value of √(xy) is?
Show answer & explanation
Correct answer: D
Explanation
Correct Answer is option 4 i.e. 7
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Concept |
Understanding |
Application |
Fair calculation |
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Divisibility rule: If a number is divisible by 72 it must be divisible by 8 and 9 Divisibility by 8: Last 3 digits must be divisible by 8. Divisibility by 9: Sum of all digits should by divisible by 9 |
Eight-digit no.: 5y5884805x6 is divisible by 72
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Last 3 digits 5x6 must be divisible by 8: Hence, x = 7 Divisibility by 9: [5 + y + 5 + 8 + 8 + 4 + 8 + 0 + 5 + 7 + 6] should be Divisible by 9. ⇒[56 + y] should be Divisible by 9. ⇒Hence, y = 7 Hence, √xy = √7×7 = 7 |
√49 = 7 |