Of the three numbers, first is twice the second and second

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Of the three numbers, first is twice the second and second is twice the third. The average of three numbers is 21. The smallest of the three numbers is

Let the third number be n.
∴ The second number = 2n
and the third number = 2 × 2n = 4n

According to the question,	4n + 2n + n	= 21
	3

⇒ 7n = 21 × 3

⇒ n =	21 × 3	= 9
	7

Second method to solve this question :
a = 2, b = 2, y = 21

First number =	3ab	y
	1 + b + ab

First number =	3 × 2 × 2	× 21
	1 + 2 + 4

First number =	12	× 21 = 36
	7

Second number =	3b	y
	1 + a + ab

Second number =	3 × 2	× 21 = 18
	7

Third number =	3	y
	1 + a + ab

Third number =	3	× 21 = 9
	7