A two-digit number is such that the product of the digits is 8. When 18 is added to the number, then the digits are reversed. The number is:
A). 18
B). 24
C). 42
D). 81
24
Let the ten's and unit's digit be x and 8/x respectively.
Then,
(10x + 8/x) + 18 = 10 * 8/x + x
9x2 + 18x - 72 = 0
x2 + 2x - 8 = 0
(x + 4)(x - 2) = 0
x = 2
So, ten's digit = 2 and unit's digit = 4.
Hence, required number = 24.
1. If one-seventh of a number is 55 then 40% of that number = ?
3. What is the least number to be added to 3006 to make it a perfect square?
5. If the difference between the squares of two consecutive numbers is 47, what is the smaller number ?
6. If 272/3 × 81-1/2 = 3x, the value of x is
7. What is the remainder when product of 2256, 3089, 5098 is divided by 17?
8. The cost of 87 pens and 29 pencils is `783. What is the cost of 90 pens and 30 pencils ?
9. A number when divided by 72 leaves remainder 10. What will be the same number is divided by 9?