The number of weekly hours spent on a smart device varies inversely with the person's age. If a 20-year-old person spends 52 hours on their smart device each week, how many hours does a 50-year-old person spend on their smart device?

98 hours

20.8 hours

130 hours

19.2 hours

1 answer

The relationship described can be formulated as an inverse variation, which means that if one variable increases, the other decreases proportionally. Mathematically, this can be represented as:

\[ x \cdot y = k \]

where \( x \) is the age of the person, \( y \) is the number of hours spent on the smart device per week, and \( k \) is a constant.

Given:

  • For a 20-year-old ( \( x = 20 \) ), \( y = 52 \) hours: \[ 20 \cdot 52 = k \ k = 1040 \]

Now, we need to find the number of hours a 50-year-old ( \( x = 50 \) ) spends on their smart device. We can plug \( x \) into the formula and solve for \( y \):

\[ 50 \cdot y = 1040 \]

To solve for \( y \):

\[ y = \frac{1040}{50} \ y = 20.8 \]

Thus, a 50-year-old person spends 20.8 hours on their smart device each week.

The answer is 20.8 hours.