Then, number = 10x + y.
Number obtained by interchanging the digits = 10y + x.
∴ (10x + y) + (10y + x) = 11(x + y), which is divisible by 11.
Then, 2x = 10 or x = 5. So, the number is either 253 or 352.
Since the number increases on reversing the digits, so the hundred's digits is smaller than the unit's digit.
Hence, required number = 253.
Then, unit's digit = x + 2.
Number = 10x + (x + 2) = 11x + 2.
Sum of digits = x + (x + 2) = 2x + 2.
∴ (11x + 2)(2x + 2) = 144
⟹ 22x2 + 26x - 140 = 0
⟹ 11x2 + 13x - 70 = 0
⟹ (x - 2)(11x + 35) = 0
⟹ x = 2.
Hence, required number = 11x + 2 = 24.
Then, x + y = 25 and x - y = 13.
4xy = (x + y)2 - (x- y)2
= (25)2 - (13)2
= (625 - 169)
= 456
∴ xy = 114.
∴ Required number of ways | = (7C3 x 6C2) + (7C4 x 6C1) + (7C5) | |||||||||||
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= (525 + 210 + 21) | ||||||||||||
= 756. |
Required number of words | = Number of arrangements of 10 letters, taking 4 at a time. |
= 10P4 | |
= (10 x 9 x 8 x 7) | |
= 5040. |
Let the ten's and unit digit be x and | 8 | respectively. |
x |
Then, | ❨ | 10x + | 8 | ❩ | + 18 = 10 x | 8 | + x |
x | x |
⟹ 10x2 + 8 + 18x = 80 + x2
⟹ 9x2 + 18x - 72 = 0
⟹ x2 + 2x - 8 = 0
⟹ (x + 4)(x - 2) = 0
⟹ x = 2.
Then, xy = 9375 and | x | = 15. |
y |
xy | = | 9375 |
(x/y) | 15 |
⟹ y2 = 625.
⟹ y = 25.
⟹ x = 15y = (15 x 25) = 375.
∴ Sum of the numbers = x + y = 375 + 25 = 400.
Then, (10x + y) - (10y + x) = 36
⟹ 9(x - y) = 36
⟹ x - y = 4.
Then, x + y = 15 and x - y = 3 or y - x = 3.
Solving x + y = 15 and x - y = 3, we get: x = 9, y = 6.
Solving x + y = 15 and y - x = 3, we get: x = 6, y = 9.
So, the number is either 96 or 69.
Hence, the number cannot be determined.
Then, | 1 | of | 1 | of x = 15 ⟺ x = 15 x 3 x 4 = 180. |
3 | 4 |
So, required number = | ❨ | 3 | x 180 | ❩ | = 54. |
10 |
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