Q1 of 55 Page 80

If 5x6 is exactly divisible by 3, then the least value of x is

We know that if sum of digits of a number is divisible by 3, then the number is divisible by 3.


Here,


5 + x + 6 = multiple of 3


∴ 11 + x = 0, 3, 6, 9, ….


Hence,


11 + x = 12


∴ x= 1


the least value of x is 1

More from this chapter

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13

Fibonacci numbers Take 10 numbers as shown below:

a, b, (a + b), (a + 2b), (2a + 3b), (3a + 5b), (5a + 8b), (8a + 13b), (13a + 21b), and (21a + 34 b). Sum of all these numbers =11(5a + 8b) = 1 1 x 7th number.


Taking a = 8, b =13; write 10 Fibonacci numbers and verify that sum of all these numbers =11 x 7th number.

 14

Complete the magic square:




























14




0



8




6



11



4





7




2



1



12


 2

If 64y8 is exactly divisible by 3, then the least value of y is

 3

If 7x8 is exactly divisible by 9, then the least value of x is