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News from Mathnasium of Coral Springs / Parkland

Problem of the Week 05-15-2017

May 15, 2017

Lower Elementary:

Question: Did you know that goldfish memories last for 180 days and that they can recognize faces? If Mrs. Olson sends her 1st grade class’s goldfish to live with one of her students for the summer, will it recognize her 3 months later when the student brings it back to school?

Solution:  A month is about 30 days. So, 3 months is about 30 + 30 + 30 = 90 days. Since 90 days is less than 180 days, the goldfish will still recognize Mrs. Olson.

Upper Elementary:

Question: Terry has a goldfish that is 3¼ inches long. Margot has a goldfish that is 3.3 inches long. Who has the bigger goldfish?

Solution:  To solve this problem, we can convert 3¼ to a decimal. A fourth is equal to 0.25, so Terry’s fish is 3.25 inches long. That means that Margot’s fish is bigger because 3.3 is more than 3.25.

Middle School:

Question: An aquarium is 24 inches long, 12 inches wide, and 16 inches tall. What is the volume of the aquarium?

Answer:  4,608 cubic inches

Solution:  If we multiply the length by the width, we get the area of the base of the aquarium: 24 × 12 = 288 square inches. If we multiply the area of the base by the height, we get the volume: 288 × 16 = 4,608 cubic inches.

Algebra and Up:

Question: Sebastian wins a 0.5 inch long goldfish at a county fair. Every year, the goldfish’s length increases by 25%. The goldfish lives for 21 more years. Write an equation for the length of the fish x in terms of the number of years t that have passed since the county fair.

Answer:   x = 0.5(1.25)t

Solution:  Every year, the length of the goldfish is multiplied by 1.25. Since the additional length compounds, we’re going to need to multiply by 1.25 a number of times equal to the number of years since the fair. So we’re going to raise our 1.25 to the power of t. This gives us x = 0.5(1.25)t.