Question

The table shows that Marta's heart beats 18 times every 15 s. Use equivalent ratios to complete the table. Explain how you found the time in seconds for 180 heartbeats.

Answer 1

(a) 36 and 90

(b)150 times

Step-by-step explanation:

In 15 seconds, Martha's heart beats 18 times.

Thus:

`In\text{ 1 second, Martha's heart beats }(18)/(15)\text{ times}`

Therefore:

`\begin{gathered} In\text{ 30 seconds, Martha's heart beats }(18)/(15)*30=36\text{ times} \\ In\text{ 45 seconds, Martha's heart beats }(45)/(15)*30=90\; \text{times} \end{gathered}`

(b)If the number of heartbeats = 180

We use the ratio in the first row:

`\begin{gathered} (15)/(x)=(18)/(180) \\ (15)/(x)=(1)/(10) \\ x=15*10 \\ x=150\text{ seconds} \end{gathered}`

Then, the number of seconds will be 150 seconds.