The diagram below shows the percentage of their total sleep that men and women spend in deep sleep, depending on their age in years, A - Junior Cycle Mathematics - Question 3 - 2021

If Gina spends 16% of her total sleep in deep sleep and sleeps an average of 8 hours each night:

Total sleep each week = 8 hours/night * 7 nights = 56 hours/week.

Hours spent in deep sleep per week = 0.16 * 56 = 8.96 hours.

Therefore, Gina spends approximately 9 hours in deep sleep each week.

From the graph, we can see that women spend a lower percentage of their sleep in deep sleep compared to men for ages 10 < A < 50. Thus, the inequality is: 10 < A < 50.

6 billion can be written as 6 x 10^9.

To estimate the percentage of total sleep spent in deep sleep for age 60, we can note the pattern in the decreasing percentages:

From 40 (15.0) to 45 (13.6) shows a decrease of 1.4.

From 45 (13.6) to 55 (12.2) shows a decrease of 1.4 as well.

Assuming the same decrease, for age 60: 12.2 - 1.4 = 10.8. Thus:

The slope of -0.14 indicates that for every additional year of age, the percentage of total sleep spent in deep sleep decreases by 0.14%. This means that as men age, they tend to spend less of their total sleep in deep sleep.