The GED test sometimes shows a picture of something with marks on it, a ruler, a thermometer, a measuring cup, a gauge, or a number line, and asks what it reads. The hard part is almost never the numbers that are printed. It is the small marks between them, which have no numbers at all. This page is about those.
The one method
Every scale works the same way, whatever it measures.
- Find two labeled marks next to each other.
- Subtract to find how far apart they are.
- Count the spaces between them. Count spaces, not marks: 4 small marks in between make 5 spaces.
- Divide. That is what one small space is worth.
value of one space = (difference between two labels) ÷ (number of spaces)
Worked example. On this thermometer the labels 20 and 30 are 10 degrees apart, and there are 5 spaces between them. So each space is 10 ÷ 5 = 2 degrees. The red stops 3 spaces above 20, and 3 × 2 = 6, so it reads 20 + 6 = 26 degrees.
Check yourself: the answer must sit between the two labels it is between. 26 is between 20 and 30, so it is the right size.
Rulers
On an inch ruler, count the marks between two whole inches: 8 spaces means each is 1/8 inch, and 16 spaces means each is 1/16. On a centimeter ruler each small space is a millimeter, a tenth of a centimeter.
1.How long is the bar?
2.How long is the bar?
3.How long is the bar?
4.How long is the bar?
5.How long is the bar, in centimeters and in millimeters?
Thermometers
Find two labeled marks next to each other, subtract, and divide by the number of spaces between them. Below zero, the numbers get larger as they go down.
6.What temperature does it show?
7.What temperature does it show?
8.What temperature does it show?
9.What temperature does it show?
Cups and cylinders
Read the liquid where its flat top meets the marks. Work out the value of one small space first.
10.How much liquid is in the cylinder?
11.How much liquid is in the cylinder?
12.How much is in the cup?
Dials and gauges
A dial is a ruler bent into a circle. The method is the same: two labels next to each other, subtract, divide by the spaces between them.
13.What does the scale read?
14.How fast is the car going?
15.What pressure does the gauge show?
16.What does the kitchen scale read?
17.The tank holds 16 gallons. About how many gallons are left?
Number lines with only the ends labeled
Only the two ends are labeled. Subtract the ends and divide by the number of spaces to find what one space is worth.
18.What number is at the dot?
19.What number is at the dot?
20.What number is at the dot? Write it as a fraction.
21.What number is at the dot?
Answers
- 1. 2 3/8 inches. Each inch has 8 spaces, so each is 1/8. The bar passes 2 and goes 3 more spaces: 2 3/8.
- 2. 1 5/8 inches. 1 whole inch and 5 of the 8 spaces in the next one: 1 5/8.
- 3. 3 3/16 inches. This ruler has 16 spaces to the inch. The bar passes 3 and goes 3 more: 3 3/16.
- 4. 2 3/4 inches. It ends on the longer mark halfway between the half and the whole: 2 12/16, which is 2 3/4.
- 5. 6.4 cm, which is 64 mm. 6 whole centimeters and 4 small spaces, each a tenth of a centimeter: 6.4 cm.
- 6. 74°F. From 70 to 80 there are 5 spaces, so each is 2 degrees. The top of the red is 2 spaces above 70: 74.
- 7. −6°F. Each space is 2 degrees. The red stops 3 spaces below 0: 3 × 2 = 6 degrees below zero.
- 8. 37°C. From 35 to 40 there are 5 spaces, so each is 1 degree. It stops 2 above 35.
- 9. 45°F. From 40 to 60 there are 4 spaces, so each is 5 degrees. It stops 1 space above 40.
- 10. 325 mL. From 300 to 400 there are 4 spaces: 100 ÷ 4 = 25 mL each. It is 1 space above 300.
- 11. 65 mL. From 60 to 80 there are 4 spaces, so each is 5 mL. It is 1 space above 60.
- 12. 1 1/4 cups. Between the labels 1 and 1 1/2 there is one mark: each space is 1/4 cup. It stops at the mark above 1.
- 13. 130 pounds. From 100 to 150 there are 5 spaces, so each is 10 pounds. The needle is 3 spaces past 100.
- 14. 65 miles per hour. From 60 to 80 there are 4 spaces: 5 miles per hour each. The needle is 1 past 60.
- 15. 34 pounds per square inch. From 30 to 40 there are 5 spaces, so each is 2. The needle is 2 spaces past 30.
- 16. 650 grams. From 600 to 800 there are 4 spaces: 50 grams each. The needle is 1 space past 600.
- 17. 12 gallons. The needle is on 3/4, and 3/4 of 16 is 12.
- 18. 2.55. The ends are 0.2 apart, over 4 spaces: 0.05 each. Three spaces past 2.4 is 2.55.
- 19. −1.5. The ends are 4 apart, over 8 spaces: 0.5 each. Three spaces past −3 is −1.5.
- 20. 4/6, which is 2/3. From 0 to 1 in 6 spaces: each is 1/6. Four of them is 4/6.
- 21. 225. The ends are 150 apart, over 6 spaces: 25 each. Five spaces past 100 is 225.
More on measurement: Quiz 26, Units and Conversions, and the Family 6 page.