Question 911884
1/a+1/b=1/x
1/5+1/20=1/x
20/100+5/100=1/x
25/100=1/x
x=100/25
x=4 days working together
check
x/a+x/b=1
x/5+x/20=1
4/5+4/20=1
0.8+0.2=1
1=1
ok
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