Say 10600 is divided into positive quantities A, B, C, and D. Use the following information to find the value of D: If you remove A, the average of the other 3 numbers is 1000. If you remove B, the average of the other 3 numbers is 3220. If you remove C, the average of the other 3 numbers is 3180.
Explanation
To solve this, we define the sum of the four quantities as A+B+C+D=10600. We then convert the average information into equations:
If we remove A, the average of the remaining numbers is 1000:
3B+C+D=1000⟹B+C+D=3000
If we remove B, the average of the remaining numbers is 3220:
3A+C+D=3220⟹A+C+D=9660
If we remove C, the average of the remaining numbers is 3180:
3A+B+D=3180⟹A+B+D=9540
Now, we add these three derived equations together:
(B+C+D)+(A+C+D)+(A+B+D)=3000+9660+9540
2A+2B+2C+3D=22200
Since we know that A+B+C+D=10600, we can express the sum (A+B+C) as (10600−D). Substituting this into the combined equation:
2(A+B+C)+3D=22200
2(10600−D)+3D=22200
Expanding and solving for D:
21200−2D+3D=22200
21200+D=22200
D=22200−21200=1000
Conclusion: The value of D is 1000, which corresponds to option 4.