Question

If Dipti can eat 12eggs in x minutes, then how many eggs can she eat in y hours?
A.\[\dfrac{{720}}{{xy}}\]
B.\[\dfrac{{xy}}{{720}}\]
C.\[\dfrac{{720y}}{x}\]
D.None of the above

Answer 1

Hint: Here they have given her speed of eating in minutes and asked the speed in hours. So we need to convert the speed in hours first and then find the number of eggs she will eat. We will use a unitary method to find that.

Complete step-by-step answer:
We know that 1hour = 60 minutes
Thus x minutes = \[\dfrac{x}{{60}}\]hours.
Now we have converted minutes in hours.
Here Dipti eats 12 eggs in x minutes, that is she eats them in \[\dfrac{x}{{60}}\]hours.
We have to calculate the number of eggs she will eat in y hours.
So I will use the unitary method again.
\[
  12eggs \to \dfrac{x}{{60}}hours \\
  ?eggs \to hours \\
\]
Number of eggs she will eat in y hours
\[
   = \dfrac{{12 \times y}}{{\dfrac{x}{{60}}}} \\
   \Rightarrow \dfrac{{12 \times y \times 60}}{x} \\
   \Rightarrow \dfrac{{720y}}{x} \\
\]
So she will eat \[\dfrac{{720y}}{x}\]in y hours.
So option C is correct.

Note: Student should read the question carefully. They are given speed in one unit and asked in another unit so we have to change them in the same unit and then calculate. Here \[\dfrac{x}{{60}}\] is in the denominator of the main fraction so its denominator will go to the numerator.