Question

10. If 21y5 is a multiple of 9, where y is a digit, what is the value of y?
11. The ages of Rahul and Haroon are in the ratio 5:7. Four years later the
be 56 years. What are their present ages?
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Answer 1

Answer:

10.y=1

Step-by-step explanation:

10.A number is divisible by 9 if the sum of digits is a multiple of 9.so here, 2+1+y+5=multiple of 9, which is only possible if y=1

Answer 2

Answer:

10. If Number is Divisible by 9, then it will must be Divisible by 9. [ Divisiblity Rule : When sum of digits is Divisible by 9, then Number is Divisible by 9 ]

⇢ (2 + 1 + y + 5) Divisible by 9

⇢ (8 + y) Divisible by 9

⇢ (8 + 1) Divisible by 9

⇢ 9 Divisible by 9

• y = 1

Hence, Least Number would be 1.

11. Let ages be 5x and 7x

⇒ Sum after 4 years = 56

⇒ (5x + 4) + (7x + 4) = 56

⇒ 12x + 8 = 56

⇒ 12x = 48

⇒ x = 4

• 5x = 5(4) = 20 years

• 7x = 7(4) = 28 years