Sum of a finite geometric series, and infinite geometric series
Grade 11 Math Worksheet
Circle the best answer, or write your answer on the line.
Bo works out 5 + 15 + 45 + … + 1215 on a math club card. What is the sum?
Esme works out 486 + 162 + 54 + … + 2 on a math club card. What is the sum?
Jun works out 1024 + 256 + 64 + … + 1 on a math club card. What is the sum?
Luz writes the infinite series 48 + 12 + 3 + … on the class board. What number does its running total approach?
Ren's parents add $500 to a savings fund at the end of each year, and it grows 3% a year. To the nearest cent, what does it hold right after deposit 6?
Tala's grandparents add $100 to a savings fund at the end of each year, and it grows 5% a year. To the nearest cent, what does it hold right after deposit 10?
Zee's parents add $250 to a savings fund at the end of each year, and it grows 2% a year. To the nearest cent, what does it hold right after deposit 8?
Ari writes the infinite series 32 + 24 + 18 + … on the class board. Which statement about its total is right?
- No total, since the terms never reach 0
- Total 128/3, since 32 ÷ (3/4) = 128/3
- Total 74, the sum of the terms shown
- Total 128, since 32 ÷ (1 − 3/4) = 128
Esme writes the infinite series 16 + 20 + 25 + … on the class board. Which statement about its total is right?
- No total, since r = 5/4 and the terms keep growing
- Total 12.8, since 16 ÷ (5/4) = 12.8
- Total 61, the sum of the terms shown
- Total -64, since 16 ÷ (1 − 5/4) = -64, applying the formula anyway
Jun writes the infinite series 8 − 12 + 18 − … on the class board. Which statement about its total is right?
- Total 14, the sum of the terms shown
- Total 3.2, since 8 ÷ (1 − (-3/2)) = 3.2
- Total -16/3, since 8 ÷ (-3/2) = -16/3
- No total, since r = -3/2 and the total swings further each time