The quantity reported an <em>equivalent net</em> percentage change of 28 percent.
<h3>How to calculate the net change of a quantity in percentages</h3>
In this problem we must determine the <em>simple</em> percentage change equivalent to two <em>consecutive</em> percentual changes. The formula that describes the situation is:
1 + r/100 = (1 - 60/100) · (1 + 80/100)
1 + r/100 = 72/100
r/100 = - 28/100
r = - 28
The quantity reported an <em>equivalent net</em> percentage change of 28 percent.
<h3>Remark</h3>
The statement is incomplete. Complete form is presented below:
A quantity is changing. At first it descreased by 60 percent and it increased by 80 percent. What is net change of the quantity in percentage?
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Answer:
4/10 or 2/5
Step-by-step explanation:
9/10-1/2 = 9/10-5/10 = 4/10 = 2/5
The distance traveled by the balloon in every minute makes an arithmetic sequence with a first term equal to 40 ft and common difference equal to 20. The nth term of an arithmetic sequence is calculated by,
an = a1 + (n - 1) x d
Substituting,
an = 40 + (15 - 1) x 20 = 320
Thus, the answer is letter B. 320 feet.