Together 3

If Sally can paint a house in 4 hours, and John can paint the same house in 6 hours, how long will it take for both of them to paint the house together?

Correct answer:

t =  2.4 h

Step-by-step explanation:

$$\begin{gathered} h_1=1\mathrm{/}4={\displaystyle \frac{1}{4}}=0.25 \\ {h}_2=1\mathrm{/}6={\displaystyle \frac{1}{6}}\doteq 0.1667 \\ t={\displaystyle \frac{1}{h_1+h_2}}={\displaystyle \frac{1}{0.25+0.1667}}={\displaystyle \frac{12}{5}}={\displaystyle \frac{12}{5}}\text{ h}=2.4\text{ h} \end{gathered}$$

Try another example

Related math problems and questions:

• Garden
  Father dig up the garden in 9 hours. Son in 13 hours. How many hours take dig up the garden together?
• Soldier
  An experienced soldier digs a good trench in 30 hours. Two soldiers dug the same trench each 40 hours. How many hours will the ditch dig all three together?
• Three pumps
  We are filling the pool. The first pump would be filled in 12 hours, the second pump in 15 hours. If all three pumps were running at the same time, it would fill the pool for 4 hours. How long would the pool fill only with the third pump?
• Three painters
  The three painters have painted bridge. The first would work done in 5 days, the second in 6 days, and the third in 7.5 days. How long will the bridge work if they work together?
• Cleaners
  Milan would clean up the room for 2.5 hours, Eric would take 10 hours. How long they swept the room together?
• Six painters
  Six painters paint an area of 120 m² in 4 hours. How long does it take for 12 painters to paint 480 m² with the same performance?
• Painters
  First painter painted fence himself for 4 hours, the second painter 1.2 hours sooner than first, and the third painters slowest up to 16 hours. How long took them paint fence if worked together?
• Three pumps
  The water tank is emptied with the first pump in 6 hours, with the second pump in 2 hours. In order to be emptied in 1 hour, all three pumps had to be started at once. How long will take tank be emptied by only the third pump?
• Pumping
  The tank is filled with a larger pump in 12 hours and with scond pump in 15 hours. For how long does the tank fill when both pumps are switched on at the same time?
• Summer tires
  Three tire servants have to change the summer tires on 6 cars in 2 hours. Mark's replacement would take 4.5 hours, Jirka would do it in 3 hours and 10 minutes, and Honza in 4 hours. Will they be able to replace all tires at the desired time?
• Oil tank and pipes
  The underground oil tank can be filled by two oil pipelines. The first is filled in 72 hours and the second in 48 hours. How many hours from the moment when first pipeline began to fill the oil is it necessary to start filling it with the second to fill i
• Parquet floor
  Three workers laid parquet floor for 2.301 hour. The first one would do this work alone 7 hours, the second in 6 hours. For how many hours would fulfill this work the third worker, if he worked alone?
• In and out
  The empty tank is filled in 12 minutes and empty in 16 minutes. How long does it take to fill if we forgot to close the drain? If the tank has 1000 l.
• A report
  Maricris can type a committee report in 5 hours. Jane helped Maricris and together they finished the report in 3 hours. How long would it take Jane to complete the report she had worked alone?
• Two pumps
  The first pump fills the tank in 24 hours second pump in another 40 hours. For how long will it take to fill the tank if it operates both pumps at the same time?
• Our house
  Our house would paint four painters in 14 days. How long could it paint five painters? How long will it take if two other painters will come to help after 5 days?
• Mow the lawn
  Dano would mow the lawn in 12 hours and Milada in 16 hours. How long will take the lawn mow together?