Choosing the Correct Units of Measure | 2nd Grade PDF Measurement ... - Free Printable

Let's solve each question in Section A: Measuring Length and explain the reasoning behind each answer.

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1) Which one is 5 mm long?

- An ant ✔
- Your arm ✘ (much longer, about 60–70 cm)
- A bus ✘ (about 10–15 meters)

Explanation:
A millimeter (mm) is a very small unit. 5 mm is about half a centimeter. An ant is typically around 3–6 mm long, so an ant is the correct choice.

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2) Which one is 15 cm long?

- A football pitch ✘ (about 100 meters)
- A mobile phone ✔
- A dog ✘ (a typical dog is 50–100 cm long)

Explanation:
15 cm is about the size of a smartphone. Most smartphones are between 14–16 cm long, so a mobile phone is the best match.

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3) Which one is 20 m long?

- A tennis court ✘ (a standard tennis court is about 23.77 m long)
- A toothbrush ✘ (about 20–25 cm)
- A car ✔

Explanation:
20 meters is quite long. A car is usually about 4–5 meters long, but a large vehicle like a bus or truck might be closer to 20 m. However, among the choices, a car is too short — wait! Let’s double-check:

Actually, a tennis court is about 23.77 meters long, which is close to 20 m. But the options are:

- A tennis court → ~24 m
- A toothbrush → ~20 cm
- A car → ~4–5 m

Wait — none are exactly 20 m. But a tennis court is closest to 20 m. So likely the intended answer is a tennis court, even though it's slightly over.

But let's look again: Is there a better option?

No — a car is only 4–5 m. Toothbrush is 20 cm. So perhaps the question meant "around 20 m"? Then a tennis court is the best fit.

✔ Correct answer: A tennis court

> Note: The actual length of a singles tennis court is 23.77 m, which is close enough for estimation in this context.

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4) How would you measure...?

We choose the most appropriate unit: mm, cm, or m

#### a) A giraffe?
- □ mm ✘ (too small)
- □ cm ✘ (still too small; 1 cm = 0.01 m)
- ✔ m (giraffes are 4–6 meters tall)

Answer: m

#### b) A pencil?
- □ mm ✘ (too precise, not practical)
- ✔ cm (pencils are 15–20 cm long)
- □ m ✘ (too big)

Answer: cm

#### c) A house?
- □ mm ✘
- □ cm ✘
- ✔ m (houses are 10–20 meters wide/long)

Answer: m

#### d) Your height?
- □ mm ✘ (too detailed)
- ✔ cm (people are measured in centimeters, e.g., 150 cm, 170 cm)
- □ m ✘ (we say 1.7 m, but usually use cm for precision)

Answer: cm

#### e) A cereal box?
- □ mm ✘
- ✔ cm (cereal boxes are about 30–40 cm tall)
- □ m ✘

Answer: cm

#### f) A screw?
- ✔ mm (screws are small; e.g., 10 mm, 20 mm)
- □ cm (possible, but less precise)
- □ m ✘

Answer: mm

#### g) A newborn baby?
- □ mm ✘
- ✔ cm (newborns are about 50 cm long)
- □ m ✘ (would be 0.5 m, but we use cm)

Answer: cm

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✔ Final Answers:

#### Section A: Measuring Length

1) An ant
2) A mobile phone
3) A tennis court
4)
a) m
b) cm
c) m
d) cm
e) cm
f) mm
g) cm

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🔍 Summary of Units:

- mm (millimeter): Very small objects (nails, screws, insects)
- cm (centimeter): Medium-sized objects (pencils, phones, babies)
- m (meter): Large objects (cars, houses, animals like giraffes)

This worksheet teaches estimation and appropriate unit selection based on real-world size.

Let me know if you'd like this as a printable answer key!