Copier X prints at a rate of 80 letters in every 5 minutes and Copier Y prints at a rate of 156 letters in every 4 minutes. At 4 p.m., both copiers started printing. After a while, Copier X stopped printing for some time as the ink cartridges were being changed before it continued to print again. Copier Y continued printing during this time. At 6 p.m., the total number of letters printed during the past two hours was 7209. Express the number of letters printed by Copier X 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 X prints per min = 80 ÷ 5 = 16
Number of letters Copier Y prints per min = 156 ÷ 4 = 39

From 4 p.m. to 6 p.m. = 2 h
1 h = 60 min
2 h = 120 min

Number of letters printed by Copier Y in 4 h
= 120 x 39
= 4680

Number of letters printed by Copier X in 4 h
= 7209 - 4680
= 2529

Percentage of the number of letters that Copier X printed over the total number of letters printed
= ²⁵²⁹₇₂₀₉ x 100%
≈ 35.08%

Answer(s): 35.08%