PencilGo

Grade 8 · Math

8th grade Why a line has the same slope everywhere (similar triangles) worksheet

6 printable versionsChallenge Me10 questions · answer keyFree · no account

Level: Building Confidence · On Level · Challenge Me

When it’s done, scan the sheet with your phone and PencilGo marks it and picks the next one. Create a free account

Version
Print

Why a line has the same slope everywhere (similar triangles)

Grade 8 Math Worksheet - Challenge Me

NameDate

Circle the best answer, or write your answer on the line.

  1. Bo's sunflower grows at a steady rate and was already tall at day 2. Points A and B are marked. How tall is it at C, on day 10?

  2. Jun's toy ramp rests on a stack of books. Points A and B are marked on its side view. How high is the ramp at C, 16 inches across?

  3. Kira starts a bike ride some miles from home at a steady speed. Points A and B are marked. How many miles from home is Kira at C, after 5 hours?

  4. Luz's sunflower grows at a steady rate. Points A and B are marked on its height graph. On which day, at C, is it 35 inches tall?

  5. Milo's tub already holds some water when the circle runs at a steady rate. Points A and B are marked on the graph. At what time, at point C, does the tub hold 24 gallons?

  6. Tala's sledding hill has slope 0.4. A slope triangle under it has run 6.5 meters. What is its rise, in meters?

  7. Zee's snail graph is a straight line through (0, 0). Its slope triangle has run 3/4 minute and rise 5/6 inch. What rule gives y (inches) for any x (minutes)?

  8. The given slope triangle on Esme's roof has run 8 inches and rise 5 inches. A smaller triangle on the roof is half the size of the given one. What is the roof's slope?

  9. A slope triangle on Jun's sledding hill has run 10 feet and rise 3 feet. A bigger triangle on the same hill is 3/2 times as big. What is the slope of the hill?

  10. Luz says: "A longer slope triangle on the same ramp has a bigger slope." Which reply is right?

    • No: all slope triangles on the ramp are similar, so rise ÷ run is the same
    • Yes: the slope is bigger near the top of the ramp
    • No: the slope is the same because the long sides match each other along the ramp
    • Yes: a longer triangle rises more, so its slope is bigger
PencilGopencilgo.com

8th grade Why a line has the same slope everywhere (similar triangles) worksheet – printable
Print: 123456

About this worksheet

Slope from similar triangles. Every version has 10 questions, and the answer key prints on the second page.

What your child will learn

  • I can use a small slope triangle to find a missing rise or run on a bigger one, because both sit on the same line.
  • I can say why every slope triangle on a straight line gives the same slope, and I know a bigger triangle does not make the slope bigger.
  • I can write the rule y = mx for a line through (0, 0), and find a point on a line that starts above zero by scaling a triangle from a point I know.

Standard: 8.EE.B.6 (slope part)

Words to know

slope triangle: A right triangle under a line: its flat side is the run, its upright side is the rise.

similar triangles: Same shape, different size: both sides are multiplied by the same number.

scale factor: The number that turns the small triangle's sides into the big one's.

slope: The rise for each 1 of run. For any triangle on the line it is rise ÷ run.

y = mx: The rule for a line through (0, 0): y is the slope m times x.

Common mistakes

Your child added the same amount to both triangle sides instead of multiplying. Try it with a photo that is doubled: if a picture is 4 wide and 3 tall, how tall is the copy that is 8 wide?

Your child divided by the scale factor when the bigger triangle needs multiplying.

Your child kept the right numbers but swapped run and rise.

What to say

Ask: is the big triangle's side bigger or smaller than the small one's?

Ask: in a slope, which number goes on top, the rise or the run?

Questions parents ask

What is the most common mistake with why a line has the same slope everywhere (similar triangles)?

Your child added the same amount to both triangle sides instead of multiplying. Try it with a photo that is doubled: if a picture is 4 wide and 3 tall, how tall is the copy that is 8 wide?

Are these 8th grade math worksheets free to print?

Yes. All 6 printable versions at each level are free to print, with the answer key, and no account is needed.

More grade 8 math

See all grade 8 math

Every sheet you scan goes into your child’s record: dated, marked and ready for the year-end portfolio. Homeschool records