Question
A two-digit number has digits summing up to 10. On
subtracting 36 from the number, the digits get interchanged. What is the original number?Solution
ATQ,
Let the ones digit = 'a', tens digit = 'b'
Number = 10b + a, Reversed = 10a + b
a + b = 10 --------- (I)
10b + a - 36 = 10a + b
⇒ 9b - 9a = 36
⇒ b - a = 4 --------- (II)
Add (I) and (II):
a + b + b - a = 10 + 4
⇒ 2b = 14 ⇒ b = 7
Then a = 3
Required number = 10 × 7 + 3 = 73
12    48      192      ?      3072       12288
...6400, 1600, ?, 80, 16, 4
11          20          ?             64          112        192
...What will come in place of the question mark (?) in the following series?
325, 292, 262, 229, ?, 166
48   49    45     54    ?      63      27
...Find the missing number in the given number series.
3, 7, 18, 38, 69, ?96 48 24 ? 6 3
...99, 101, 107, 131, 251, ?
16, 15, 24, -1, 48, ?
23, 28, 38, 49, 62, ?
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