Question

A scientist is doing study on person sleep. He classifies sleep activity in four stages: $1,2,3$ and $4$. Stage $3$ is the only stage considered to be deep sleep.

Ajay goes to clinic for sleeping brainwashes analyzed. Doctor monitored the person's brainwashes in $15-$minute intervals, for $8$ continuous hours, and categorized them into one of the four stages. The graph above shows this study.

Based on the graph, how many minutes did ajay spend in non-deep sleep over the course of the entire night?

Answer 1

Total number of $15-$minute interval in 8 hours $=\frac{8\times 60}{15}=32$.

Now from the graph, we can observe that Ajay achieves Stage $3$ sleep $12$ times in $8$ hours.

Hence, the total number of times he was in non-deep sleep is $32-12=20$ times.

Therefore, total time spent in non-deep sleep is $20\times 15$ minutes $=300$ minutes