Chau completed 40% of his deliveries
To find out the percentage, divide the smaller number (34) by the larger number (85) which will give you a number with a decimal
34 / 85 = 0.4
Now convert the decimal into a percent by multiplying it by 100 or moving the decimal place 2 spaces to the left
0.4 * 100 = 40%
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To check if your answer it correct, convert the percent into a decimal (40% = 0.4) and multiply it by 85. It should give you 34
0.4 * 85 = 34
Hope this helped :D