Question

3道数学题,初一下学期的,1.甲.乙两种银块分别含银80%和60%,应各取多少克,溶化后才能得到含银74%的银块500克

Answer 1

1.二元一次方程组:

x + y = 500

(0.8x + 0.6y)/(x + y)= 0.74

x=350 y=150

2.还是二元一次方程组:

x + y = 16

15x = 5y

x=4 y=11

3.一样

(4/7)x + (7/16)y = 82

(3/7)x + (9/16)y = 84

x=70 y=96