Solutions
- Anna and Carlos need to make the dinners. Bill and Dianne need to make the desserts.
- Anna and Carlos can each make 30 dinners in an hour.
\[\begin{align} \dfrac{30}{180}+\dfrac{30}{180}&= \dfrac{1}{t} \\\\ \dfrac{1}{6}+\dfrac{1}{6} &= \dfrac{1}{t} \\\\ t+t &= 6 \\\\ t &= 3 \end{align}\]
It will take Anna and Carlos 3 hours to make all the dinners.
Bill can make 40 desserts in an hour. Dianne can make 60 desserts in an hour.
\[\begin{align} \dfrac{40}{180}+\dfrac{60}{180}&= \dfrac{1}{t} \\\\ 2t+3t &= 9 \\\\ 5t &= 9 \\\\ t &= 1\dfrac45 \end{align}\]
It will take Bill and Dianne 1 hour and 48 minutes to make all of the desserts. When they are done, they can help with the dinners.
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