21. If (a2 - b2) ÷ (a + b) = 25, then (a - b) = ?
22. The sum of the digits of a natural number (10n - 1) is 4707, where n is a natural number. The value of n is :
23. The sum of digits of a two-digit number is 12 and the difference between the two-digits of the two-digit number is 6. What is the-digit number ?
24. 7386038 is divisible by :
25. The number of terms between 11 and 200 which are divisible by 7 but not by 3 are :
26. Unit's digit in (784)126 + (784)127 is :
27. If n is any positive integer, 34n - 43n is always divisible by :
28. When 10025 - 25 is written in decimal notation, the sum of its digits is :
29. Which is the greatest 5-digit number exactly divisible by 279 ?
30. If p,q,r are all real numbers then (p - q)3 + (q - r)3 + (r - p)3 is equal to :
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