The average weekly number of robots produced by Factory B and C is 3211. The average weekly number of robots produced by Factory B and D is 6356. If Factory C produced ⁴₉ as many robots as Factory D each week, how many robots does Factory B produce weekly?
Total robots that Factory B and Factory C produced
= 3211 x 2
= 6422

Total robots that Factory B and Factory D produced
= 6356 x 2
= 12712

Number of robots produced by Factory C = 4 u
Number of robots produced by Factory D = 9 u

Factory B's toys + 4 u = 6422 --- (1)
Factory B's toys + 9 u = 12712 --- (2)

(2) - (1)
9 u - 4 u = 12712 - 6422
5 u = 6290
1 u = 6290 ÷ 5 = 1258

Number of robots produced by C
= 4 u
= 4 x 1258
= 5032

Number of robots produced by B
= 6422 - 5032
= 1390

Answer(s): 1390