A contractor combined x tons of a gravel

[sahilchaudhary]

A contractor combined x tons of a gravel mixture that contained 10 percent gravel G, by weight, with y tons of a mixture that contained 2 percent gravel G, by weight, to produce z tons of a mixture that was 5 percent gravel G, by weight. What is the value of x ?

(1) y = 10

(2) z = 16

I marked C while doing this question in GMAT Prep, but OA is D.
Can anybody explain this question?

[vipulgoyal]

alligation approach
x-------z-----y
10 -5-- 5 -3--2
10 -3---5 -5--2
1.y = 10 , x & y are in ration of 3:5 hence x = 6. sufficent
2.ammount of x = 3/8*16(z resulting ammount of combined mixture)= 6, sufficent

[sahilchaudhary]

alligation approach
x-------z-----y
10 -5-- 5 -3--2
10 -3---5 -5--2
1.y = 10 , x & y are in ration of 3:5 hence x = 6. sufficent
2.ammount of x = 3/8*16(z resulting ammount of combined mixture)= 6, sufficent

I am unable to understand what you wrote.
What is alligation approach?
Could you please explain alligation approach in detail.

[vipulgoyal]

please refer below link, still have any query please let me know
https://www.beatthegmat.com/ratios-fract ... 15365.html

[sahilchaudhary]

please refer below link, still have any query please let me know
https://www.beatthegmat.com/ratios-fract ... 15365.html

Thanks man!