Correct Answer - Option 3 : 520
The ratio of first and second number is 6 : 7
The ratio of second and third number is 8 : 9
After combine both we get,
⇒ 6 : 7 : : 8 : 9
⇒ 48 : 56 : 63 ⇒ 48x, 56x and 63x.
The given difference of first and third is = 150
⇒ 63x - 48x = 150
⇒ 15x = 150
⇒ x = 10
put the value of x we get,
First number = 48x = 48 x 10 = 480
Second number = 56x = 56 x 10 = 560
Third number = 63x = 63 x 10 = 630
Average of First and second number we get,
(480 + 560)/2 = 1040/2 = 520
Hence, "520" is the correct answer.