Question P6 Number × value
Today’s problem — free all day, every step. Every day has one.
Pipe A can fill a tank in 6 hours. Pipe B can fill the same tank in 4 hours. Both pipes are turned on at the same time. How long will it take to fill the tank?
Answer
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One batch repeats. Work out one batch, then multiply.
In this one. You cannot add the times (6 h + 4 h means nothing here) — turn each time into a rate, how much of the tank is filled in one hour, because rates add and times do not.
Also uses: Same time, same distance
Items are described as a fixed group or ratio that repeats, such as tiles following a pattern, snacks sold in a fixed mix, or a rate given per hour or per item.
Children start from the grand total instead of first working out what one batch is worth. In rate questions they also confuse a duration with a clock time.
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