Multiple choice

Pipe A can fill a tank in 4 hours and pipe B can fill the same tank in 5 hours. If t is the time (in hours) that both pumps take to fill the tank, which of these equations could be used to find t?

  1. 4t + 5t = 1

  2. t/4 + t/5 = 1

  3. t/(4 + 5) = 1

  4. (4 + 5)/t = 1
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Pipe A fills 1/4 of the tank per hour, and Pipe B fills 1/5 of the tank per hour. Together, they fill (1/4 + 1/5) of the tank per hour. Over t hours, the total work done is t * (1/4 + 1/5) = 1, which simplifies to t/4 + t/5 = 1.

AI explanation

Using the combined work equation for two pipes, their individual fractions of the job completed in time t are added together and set equal to 1. This gives the equation (t/4) plus (t/5) equals 1. Therefore, the equation is t/4 + t/5 = 1.

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