Final answer:
Based on Devon's knitting rate of 40 inches per hour, statements A and C are true, with Devon knitting 40 inches per hour and adding 10 inches in 1/4 hour, respectively; while statements B and D are false, as Devon would add only 20 inches in 1/2 hour, not 30, and the rate is not 20 inches per hour.
Step-by-step explanation:
The question involves determining the truth behind several statements about Devon's knitting rate. We know that Devon knits at a constant rate and in 1/4 h, Devon adds 10 in. to a scarf. To ascertain the validity of the given statements, we need to calculate the knitting rate per hour and use it to verify each one.
Let's find Devon's knitting rate per hour: Since Devon adds 10 inches in 1/4 hour, to find the knitting rate per hour we multiply the inches knitted in 1/4 hour by 4, which gives us 40 inches per hour. Therefore, statement A is True.
If Devon knits 40 inches in one hour, then in half an hour (1/2 hour), they would knit half of 40 inches, which is 20 inches. Thus, statement B, which asserts that Devon will add 30 inches in 1/2 hour, is False.
Statement C is clearly False since we've established that Devon knits 10 inches in 1/4 hour, not 15 inches.
Lastly, statement D is incorrect as well since we've already computed the rate to be 40 inches per hour, not 20 inches per hour, making this statement False as well.