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The Extra Nine-Tenths of a Cent at the Pump

7th grade nonfiction passage about rounding gas prices: 241 words, six questions, an answer key and vocabulary.

7th grade nonfiction rounding gas prices 241 words

The Extra Nine-Tenths of a Cent at the Pump

Drive past a gas station and the sign may read $3.499 per gallon. That strange last digit is a tenth of a cent, a piece of money that no coin can pay, so how does anyone settle a bill that includes it? The answer is rounding, and the numbers show how little the extra piece actually matters.

Suppose a driver pumps 8 gallons. The pump multiplies 8 by $3.499 and gets $27.992, but money is paid in whole cents, so the amount is rounded to the nearest cent. The digit after the cents place is a 2, which is less than 5, so the total rounds down to $27.99. With 12 gallons, the product is $41.988. This time the next digit is an 8, so the cents round up, and the bill becomes $41.99.

Compare that with a sign that simply said $3.50. Twelve gallons at $3.50 would cost exactly $42.00, which is only one cent more than the real bill. A tenth of a cent per gallon is a tiny amount, and it accumulates to about a penny for every ten gallons that a customer buys.

If the difference is so small, why bother with it? Researchers who study shopping behavior have found that people tend to pay the most attention to the leftmost digits of a price. A sign showing $3.499 looks like a price in the three-forty range, even though it is nearly $3.50. Understanding rounding lets a driver see through that effect and compare stations by the real cost of filling a tank.

Questions

  1. What is the last digit in a price like $3.499 worth? in the text

  2. How are totals changed into an amount that can be paid with coins? in the text

  3. What is the bill for 8 gallons at $3.499 per gallon? in the text

  4. Why does the bill for 12 gallons round up to $41.99? in the text

  5. About how much extra does a tenth of a cent per gallon add up to? think about it

  6. Why might stations use a price like $3.499 instead of $3.50? think about it

Words to know

rounding
changing a number to a nearby, simpler one
gallon
a unit used to measure liquids such as gasoline
multiplies
uses multiplication to find a product
researchers
people who study a subject to learn new facts
leftmost
farthest to the left
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One passage, three levels

The same topic and facts written three ways, so a mixed class can read and talk about one text. Each group’s sheet shows only a shape; the key says which is which.

● Easier · 199 words · Flesch-Kincaid grade 1.6

Drive by a gas station. The sign may say $3.499 per gallon. That last digit is a tenth of a cent. No coin can pay it. So how does anyone pay a bill with it? The answer is rounding. The numbers show how small the extra piece is.

Say a driver pumps 8 gallons. The pump multiplies 8 by $3.499. That is $27.992. Money is paid in whole cents. So the amount is rounded to the nearest cent. The next digit is a 2. That is less than 5. So the total rounds down to $27.99. With 12 gallons, the answer is $41.988. This time the next digit is an 8. So the cents round up. The bill is $41.99.

Now think about a sign that said $3.50. Twelve gallons at $3.50 cost $42.00. That is just one cent more. A tenth of a cent per gallon is small. It adds up to about a penny for every ten gallons.

So why do it? Researchers who study shopping say people look at the first digits of a price most. A sign with $3.499 looks like the three-forty range. But it is almost $3.50. Knowing about rounding helps a driver see through this. Then the driver can compare stations by what a full tank really costs.

▲ This passage · 241 words · Flesch-Kincaid grade 6.4

Drive past a gas station and the sign may read $3.499 per gallon. That strange last digit is a tenth of a cent, a piece of money that no coin can pay, so how does anyone settle a bill that includes it? The answer is rounding, and the numbers show how little the extra piece actually matters.

Suppose a driver pumps 8 gallons. The pump multiplies 8 by $3.499 and gets $27.992, but money is paid in whole cents, so the amount is rounded to the nearest cent. The digit after the cents place is a 2, which is less than 5, so the total rounds down to $27.99. With 12 gallons, the product is $41.988. This time the next digit is an 8, so the cents round up, and the bill becomes $41.99.

Compare that with a sign that simply said $3.50. Twelve gallons at $3.50 would cost exactly $42.00, which is only one cent more than the real bill. A tenth of a cent per gallon is a tiny amount, and it accumulates to about a penny for every ten gallons that a customer buys.

If the difference is so small, why bother with it? Researchers who study shopping behavior have found that people tend to pay the most attention to the leftmost digits of a price. A sign showing $3.499 looks like a price in the three-forty range, even though it is nearly $3.50. Understanding rounding lets a driver see through that effect and compare stations by the real cost of filling a tank.

■ Harder · 254 words · Flesch-Kincaid grade 7.5

Drive past almost any gas station and the sign may advertise a price of $3.499 per gallon. That peculiar final digit represents a tenth of a cent, a fragment of money that no coin can actually pay. How, then, does anyone settle a bill that includes it? The answer is rounding, and the arithmetic demonstrates how little the extra fragment matters.

Suppose that a driver pumps 8 gallons. The pump multiplies 8 by $3.499 and arrives at $27.992. Because money is paid in whole cents, the amount is rounded to the nearest cent. The digit that follows the cents place is a 2, which is smaller than 5, so the total rounds downward to $27.99. With 12 gallons, the product is $41.988. On this occasion the next digit is an 8, so the cents round upward, and the bill comes to $41.99.

Compare that result with a sign that simply read $3.50. Twelve gallons at $3.50 would cost exactly $42.00, merely one cent more than the genuine bill. A tenth of a cent per gallon is a tiny amount, and it accumulates to roughly a penny for every ten gallons that are purchased.

If the difference is so negligible, why does anyone bother with it? Researchers who study shopping behavior have discovered that people tend to devote the most attention to the leftmost digits of a price. A sign showing $3.499 appears to be a price somewhere in the three-forty range, even though it is nearly $3.50. Understanding rounding allows a driver to see through that effect and to compare stations according to the real cost of filling a tank.

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How to use it

  1. Press Read it big (or B) to put the text on the projector, or Full screen (F) to fill the whole screen.
  2. Ask the questions one at a time and use Show answer when the class has decided. A shows or hides every answer.
  3. Print student copy for the class, or Print with answers for yourself.

Ideas for class

  • Before reading, put rounding, gallon, multiplies, researchers and leftmost on the board with their meanings from the Words to know section and have students predict what the text will be about.
  • Read it aloud once while students follow along, then have them reread it alone or with a partner. At a calm 100 words a minute it takes about 2 minutes to read aloud.
  • Use the Read it big button (or B) to put the text on the projector, and Show answer on one question at a time so the class commits to an answer first.
  • Question 5 asks the reader to infer. Ask students to point to the words in the passage that led them to their answer.
  • Ask students to write one question the passage did not answer, then look for the answer in a book or on a classroom screen.
  • Print the student copy for independent work and keep the answer-key copy for yourself.

Related

Questions

What reading level is "The Extra Nine-Tenths of a Cent at the Pump"?

It was written for 7th grade. It has 241 words and works out to a Flesch-Kincaid grade level of about 6.4. That is a formula's estimate from sentence length and syllables, and it is not a Lexile or a guided reading level, so check it against your students.

What do the questions ask?

There are six. 4 ask for something the text says directly and 2 ask the reader to work something out from clues. Each has an answer in the key, and the answers are written as a teacher would accept them, not as the only possible wording.

How long does it take to read?

About 2 minutes read aloud at 100 words a minute. For a one-minute fluency check, paste it into the fluency timer and use the word count.

Can I print it?

Yes. Print student copy gives the passage, the questions with lines to write on, and the word meanings. Print with answers gives the same page with the answers filled in. Both are made in your browser.

Is this passage from a published book?

No. It was written for Peabody Teach, so there is no book to buy and no login to read it.

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