Question

The ratio of clock to lamps in a library is 2:5. There are 15 lamps. How many clocks are there

Answer 1

6 clocks

Explanation;

If the ratio of clock to lamps in a library is 2:5, then the total ratio is given as;

Total ratio = 2+5

Total ratio = 7

Let the total clocks and lamps in the library be "x". If there are 15 lamps, then the total clocks and lamp is determined using the expression below;

`\begin{gathered} \frac{ratio\text{ of lamps}}{total\text{ ratio}}* x=Total\text{ lamps} \\ (5)/(7)x=15 \end{gathered}`

Cross multiply

`\begin{gathered} 5x=7*15 \\ x=7*3 \\ x=21 \end{gathered}`

Hence there are 21 clocks and lamps in the library.

Determine the total clocks there

`\begin{gathered} Total\text{ clocks}=21-total\text{ }lamps \\ Total\text{ clocks}=21-15 \\ Total\text{ clocks}=6clocks \end{gathered}`

This shows that there are 6 clocks there