Copier Y prints at a rate of 84 letters in every 2 minutes and Copier Z prints at a rate of 126 letters in every 6 minutes. At 7 p.m., both copiers started printing. After a while, Copier Y stopped printing for some time as the ink cartridges were being changed before it continued to print again. Copier Z continued printing during this time. At 10 p.m., the total number of letters printed during the past three hours was 8820. Express the number of letters printed by Copier Y as a percentage of the total number of letters printed by both copiers. Round off your answer to 2 decimal places.
Number of letters Copier Y prints per min = 84 ÷ 2 = 42
Number of letters Copier Z prints per min = 126 ÷ 6 = 21

From 7 p.m. to 10 p.m. = 3 h
1 h = 60 min
3 h = 180 min

Number of letters printed by Copier Z in 7 h
= 180 x 21
= 3780

Number of letters printed by Copier Y in 7 h
= 8820 - 3780
= 5040

Percentage of the number of letters that Copier Y printed over the total number of letters printed
= ⁵⁰⁴⁰₈₈₂₀ x 100%
≈ 57.14%

Answer(s): 57.14%