Copier K prints at a rate of 102 letters in every 2 minutes and Copier L prints at a rate of 160 letters in every 5 minutes. At 7 p.m., both copiers started printing. After a while, Copier K stopped printing for some time as the ink cartridges were being changed before it continued to print again. Copier L continued printing during this time. At 9 p.m., the total number of letters printed during the past two hours was 6435. Express the number of letters printed by Copier K 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 K prints per min = 102 ÷ 2 = 51
Number of letters Copier L prints per min = 160 ÷ 5 = 32

From 7 p.m. to 9 p.m. = 2 h
1 h = 60 min
2 h = 120 min

Number of letters printed by Copier L in 7 h
= 120 x 32
= 3840

Number of letters printed by Copier K in 7 h
= 6435 - 3840
= 2595

Percentage of the number of letters that Copier K printed over the total number of letters printed
= ²⁵⁹⁵₆₄₃₅ x 100%
≈ 40.33%

Answer(s): 40.33%