Answer:
(a) 36 and 90
(b)150 times
Explanation:
In 15 seconds, Martha's heart beats 18 times.
Thus:
[tex]In\text{ 1 second, Martha's heart beats }\frac{18}{15}\text{ times}[/tex]
Therefore:
[tex]\begin{gathered} In\text{ 30 seconds, Martha's heart beats }\frac{18}{15}\times30=36\text{ times} \\ In\text{ 45 seconds, Martha's heart beats }\frac{45}{15}\times30=90\; \text{times} \end{gathered}[/tex]
(b)If the number of heartbeats = 180
We use the ratio in the first row:
[tex]\begin{gathered} \frac{15}{x}=\frac{18}{180} \\ \frac{15}{x}=\frac{1}{10} \\ x=15\times10 \\ x=150\text{ seconds} \end{gathered}[/tex]
Then, the number of seconds will be 150 seconds.
