Copier L prints at a rate of 120 letters in every 4 minutes and Copier M prints at a rate of 120 letters in every 6 minutes. At 3 p.m., both copiers started printing. After a while, Copier L stopped printing for some time as the ink cartridges were being changed before it continued to print again. Copier M continued printing during this time. At 5 p.m., the total number of letters printed during the past two hours was 7418. Express the number of letters printed by Copier L 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 L prints per min = 120 ÷ 4 = 30
Number of letters Copier M prints per min = 120 ÷ 6 = 20

From 3 p.m. to 5 p.m. = 2 h
1 h = 60 min
2 h = 120 min

Number of letters printed by Copier M in 3 h
= 120 x 20
= 2400

Number of letters printed by Copier L in 3 h
= 7418 - 2400
= 5018

Percentage of the number of letters that Copier L printed over the total number of letters printed
= ⁵⁰¹⁸₇₄₁₈ x 100%
≈ 67.65%

Answer(s): 67.65%