You have the correct answer. It is choice B) -1/4
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Explanation:
This is because we're adding -1/4 to each term to get the next one. In other words, we're subtracting 1/4 from each term to get the next one.
- term2 = term1+(d) = 1/2 + (-1/4) = 1/2 - 1/4 = 2/4 - 1/4 = 1/4
- term3 = term2+(d) = 1/4 + (-1/4) = 1/4 - 1/4 = 0
- term4 = term3+(d) = 0 + (-1/4) = 0 - 1/4 = -1/4
- term5 = term4+(d) = -1/4 + (-1/4) = -2/4 = -1/2
and so on.
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To find the common difference, all we have to do is subtract any term from its previous one.
For example:
d = (term2) - (term1)
d = (1/4) - (1/2)
d = (1/4) - (2/4)
d = (1-2)/4
d = -1/4
The order of subtraction matters, so we cannot say d = term1-term2.
The expression that shows the total gallons is 0.5gallon/1 day*16cups/1gallon * 7days/1week
<h3>Dimensional Analysis</h3>
From the given question, we are told that Katrina drinks 0.5 gallons per day. In order to determine the total cup that she drank in a a week, we will have:
Total gallons in a week. = 0.5gallons/1 day * 7days/1
Total gallons in a week = 3.5 gallons
Since 1 gallon. = 16 cups, then;
3.5 gallons = 16cups/1gallon * 3.5gallons
3.5 gallons = 56 cups
Hence the expression that shows the total gallons is 0.5gallon/1 day*16cups/1gallon * 7days/1week
Learn more on dimensional analysis here: brainly.com/question/18559676
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I have memorized facts about fractions like these, so can tell you ...

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A fraction with 9 as a denominator is a repeating 1-digit decimal with the decimal digit being the numerator of the fraction.
A fraction with 11 as a denominator is a repeating 2-digit decimal with the two digits being 9 times the numerator of the fraction.
1/8 = 0.125, so any multiple of 1/8 is that multiple of 0.125.