Question

Show an equation and a solution for the problem. Crane A can unload a ship in 10 hours and crane B can unload it in 14 hours. How long will it take the two cranes to unload the ship working together? Round to the nearest tenth.
help please

Answer 1

Show an equation and a solution for the problem. It takes John 20 hours to paint a building. It takes Sam 15 hours to paint the same building. How long will it take for them to paint the building if they work together, with Sam starting one hour later than John? Round to the nearest tenth.
and this

Answer 2

Crane A unloads a ship at a rate of 1 per 10 hours, so \(1 \over 10\) ships per hour
Crane B unloads a ship at a rate of 1 per 14 hours, so \(1 \over 14\) ships per hour

If they both work together, they can do \({1 \over 10} + {1 \over 14} ={12 \over 70} \) ships per hour, so in t hours they will have unloaded \({12 \over 70}t\) ships.

So if they have to unload one ship, then
\[{12 \over 70}t = 1\]

where t is the amount of hours it takes them :)

Answer 3

thank you can you help with like 5 or 4 more please

Answer 4

I can help with the second one you posted but after that I have to go :)

Answer 5

ok

Answer 6

Show an equation and a solution for the problem. How much water must be added to 12 L (liters) of a 40% solution of alcohol to obtain a 30% solution?
Question 6 answers

Answer 7

John paints at a rate of \({1 \over 20}\) buildings per hour,
Sam at a rate of \(1 \over 15\) building / hour

Sam starts 1 hour later than john, so if we set t as the time john painted, then sam painted for t - 1 hours
So after t hours:
John has painted \({1 \over 20}t\) buildings
Sam has painted \({1 \over 15}(t-1)\) buildings

Together they need to paint one building so:
\[{1 \over 20}t + {1 \over 15}(t - 1) = 1\]
\[{1 \over 20}t + {1 \over 15}t - {1 \over 15} = 1\]
\[{7 \over 60}t = {16 \over 15}\]