Question

Solve these word problems. Explain and show how you got your answer.

Answer 1

Number 1. So the duck's OWN speed (if flying without any wind) with the wind behind him is: 
 Where x/10 is the wind speed 
The duck's OWN speed (if flying without any wind) with the wind against him is: 
 Where x/10 is the wind speed Remember  
So we have two equations that must equal each other since they both represent the duck's speed. 
 We need to rearrange to find x 

 Add x/10 to both sides and subtract (1600/10 from both sides gives: 

 
so x must be 400/10 which 40 metres per minute. 

Number 2.  let s=salmon and c=current 
upstream __ s-c=100m/20 min __ s-c=5m/min 


downstream __ s+c=100m/8min __ s+c=12.5m/min 

adding the two equations __ s-c+(s+c)=5+12.5 __ 2s=17.5 __ s=8.75m/min 

substituting __ 8.75+c=12.5 __ c=3.75m/min