Chapter 15 Exam

Of 420 club members, 84 signed up. What percent of the club is that?

The assigned question is: “Of 420 club members, 84 signed up. What percent of the club is that?” A learner wrote: “I used tenths as the percent base instead of hundredths for the portion involving 420, giving 21%.” Identify a concrete invalid step or assumption. Work out the correct result and explain why it is valid.

Two labels show 30% and 3/10. Decide whether they describe the same fraction of a whole.

The assigned question is: “Two labels show 30% and 3/10. Decide whether they describe the same fraction of a whole.” A learner wrote: “I reduced only the numerator of the percent fraction involving 30, and wrote No; the two claims cannot agree..” Identify a concrete invalid step or assumption. Work out the correct result and explain why it is valid.

A technician reads 0.4 of capacity and labels it 4%. Is that accurate?

The assigned question is: “A technician reads 0.4 of capacity and labels it 4%. Is that accurate?” A learner wrote: “0.4 × 100 = 41. I used this intermediate value to finish the assigned problem.” Identify a concrete invalid step or assumption. Work out the correct result and explain why it is valid.

One bar shows 1/2 of a whole, another claims that means 55% of the whole. Decide which is correct.

The assigned question is: “One bar shows 1/2 of a whole, another claims that means 55% of the whole. Decide which is correct.” A learner wrote: “I treated the fraction from 1 as a proportion of ten parts instead of a whole of 100 percent; I gave 51%.” Identify a concrete invalid step or assumption. Work out the correct result and explain why it is valid.

A claim says that 60% of 500 equals 310. Check using a fixed original whole.

The assigned question is: “A claim says that 60% of 500 equals 310. Check using a fixed original whole.” A learner wrote: “I used the percentage itself as the whole rather than the original amount involving 60, giving Yes; the original statement is correct..” Identify a concrete invalid step or assumption. Work out the correct result and explain why it is valid.

A revised fee is $884 after a 70% increase. What was the original base?

The assigned question is: “A revised fee is $884 after a 70% increase. What was the original base?” A learner wrote: “I used the final value, not the original base involving 884, in the percentage calculation and wrote $521.” Identify a concrete invalid step or assumption. Work out the correct result and explain why it is valid.