<em>D</em><em>:</em><em> </em><em>She</em><em> </em><em>needs</em><em> </em><em>to</em><em> </em><em>keep</em><em> </em><em>going</em><em> </em><em>to</em><em> </em><em>find</em><em> </em><em>more</em><em> </em><em>digits</em><em>.</em>
B and c are the speeds of the boat (in still water) and the current.
Traveling with the current, the boat goes b+c km per hour.
1 hour * (b+c km)/hour = 15 km
b+c = 15
Traveling against the current, the boat goes b-c km per hour.
3 hours * (b-c km)/hour = 15
b-c = 5
Add the two equations
b = 10 km per hour
Answer:
percent of iron in alloy= 100-42 = 58%
weight of the iron = 55×58÷100= 31.9
weight of iron= 31.9 kg
weight of copper= 55-31.9=23.1
weight of copper = 23.1
Step-by-step explanation:
[ I'm not sure but I think this is right ]
