+0  
 
+1
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5
avatar+493 

One knight can storm a castle in 15 days. He and his partner can do it in 10 days. How long does it take the partner to storm the castle alone?

cool

ant101  May 13, 2018
 #1
avatar+867 
+2

If a knight can storm a castle in 15 days, he can storm 1/15 of a castle in one day. 

If he and his partner can do it in 10 days, they can storm 1/10 of a castle in one day. 

 

We can set up the equation: 

 

\(\frac{1}{15}+\frac{1}{x}=\frac{1}{10}\\x=30\)

 

It will take his partner 30 days to storm the castle alone. 

 

I hope this helped,

 

Gavin

GYanggg  May 13, 2018
 #2
avatar+2765 
+1

knight=1/15

kinght+partner=1/10

partner=1/10-1/15=1/30

partner=30 days

smileysmiley

tertre  May 13, 2018
edited by tertre  May 13, 2018
 #3
avatar+493 
+1

Thanks, Gavin, and tertre!

smiley

ant101  May 13, 2018
 #4
avatar+867 
+2

No problem, glad I can help!

GYanggg  May 13, 2018
 #5
avatar+2765 
+1

Here to solve questions,

smiley smiley

Here's a similar problem to think of:

One elephant can eat 2000 pounds of grass in 20 days.

He and his friend can eat it in 10 days.

How long does it take for the elephant's friend to eat alone?

Solution:

Again, elephant 1:1/20

elephant + friend: 1/10

 

Equation: 1/20+x=1/10

Take 1/20 to the other side, to get: 1/10-1/20=2/20-1/20=1/20 days

So, his friend can eat the grass alone in \(\boxed{20}\) days.

 ---------------------------------------------------------------------

Here's a different type of problem to think of.

A person can finish a poster completely in 20 minutes. His friend can finish the same poster in 10 minutes. How many minutes will it take if they work together:

1/20+1/10=1/20+2/20=3/20

1(whole)/3/20=20/3=\(6 \frac{2}{3}\)minutes.

smileysmiley

tertre  May 13, 2018
edited by tertre  May 13, 2018

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