When Jose installs a new app on his phone, it creates a square icon on his home screen. The square starts with side lengths of 1 cm. The side lengths grow by 2.8 cm each second until the square reaches its maximum size. What is the perimeter of the square after 1 point 5 seconds? Recall that the perimeter of a shape is the sum of its side lengths.
In 1.5 seconds, each side grows by 2.8 × 1.5 = 4.2 cm. Adding the starting side length gives 1 + 4.2 = 5.2 cm. A square has four equal sides, so its perimeter is 4 × 5.2 = 20.8 cm, which is choice B.
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