Magnification — answer key

1. MQ1 · Practice

Model answer. actual size = image size ÷ magnification = 60 mm ÷ 300 = 0.2 mm.

Checked automatically

• Actual length: 0.2 mm (within ±2%)
  • Common wrong answer 18000 : You multiplied. The real cell is smaller than its image: divide the image size by the magnification.
  • Common wrong answer 5 : You divided the magnification by the image size. Divide the image size (60 mm) by the magnification (300).

A full answer includes

• I divided: 60 mm ÷ 300.
• actual length = 0.2 mm.

Also accept

• 0.2 mm (0.20 mm)

Watch for

• “Multiply the image size by the magnification.” — That gives 18 000 mm, far bigger than the drawing. The real cell is smaller than its image, so divide.

2. MQ2 · Practice

Model answer. magnification = image size ÷ actual size = 45 mm ÷ 0.15 mm = ×300. Magnification has no unit.

Checked automatically

• Magnification (no unit): 300 (within ±2%)
  • Common wrong answer 0.0033 : You divided the actual size by the image size. Put the image size on top: 45 ÷ 0.15.

A full answer includes

• I divided 45 mm by 0.15 mm.
• magnification = ×300 (no unit).

Also accept

• 300 (×300)

Watch for

• “Magnification is in mm.” — The units cancel when you divide mm by mm, so magnification has no unit: write ×300.

3. MQ6 · Practice

Model answer. 30 µm ÷ 1000 = 0.03 mm.

Checked automatically

• Width: 0.03 mm (within ±2%)
  • Common wrong answer 30000 : You multiplied by 1000. To change µm into mm, divide by 1000.

A full answer includes

• I divided by 1000: 30 ÷ 1000.
• 0.03 mm.

Also accept

• 0.03 mm

Watch for

• “Multiply by 1000 to change µm into mm.” — That gives 30 000 mm, thirty metres. A millimetre is a thousand times bigger than a micrometre, so divide.

4. MQ3 · Practice

Model answer. 0.06 mm × 1000 = 60 µm.

Checked automatically

• Width: 60 µm (within ±2%)
  • Common wrong answer 0.00006 : You divided by 1000. There are 1000 µm in each mm, so multiply: 0.06 × 1000.

A full answer includes

• I multiplied by 1000: 0.06 × 1000.
• 60 µm.

Also accept

• 60 µm

Watch for

• “Divide by 1000 to get micrometres.” — A micrometre is smaller than a millimetre, so there are more of them: multiply by 1000.

5. MQ4 · Practice

Model answer. (a) actual size = 32 mm ÷ 4000 = 0.008 mm. (b) 0.008 mm × 1000 = 8 µm.

Checked automatically

• (a) Actual diameter in mm: 0.008 mm (within ±2%)
  • Common wrong answer 128000 : You multiplied. Divide the image size by the magnification.
• (b) Actual diameter in µm: 8 µm (within ±2%)
  • Common wrong answer 0.000008 : You divided by 1000. To change mm to µm, multiply by 1000.

A full answer includes

• (a) 32 mm ÷ 4000 = 0.008 mm.
• (b) 0.008 mm × 1000 = 8 µm.

Also accept

• (a) 0.008 mm; (b) 8 µm

Watch for

• “Divide by 1000 to change mm into µm.” — Multiply: 1 mm is 1000 µm.

6. MQ5 · Practice

Model answer. b. actual size = image size ÷ magnification (from magnification = image size ÷ actual size).

A full answer includes

• I chose b.

Also accept

• b

Watch for

• “actual size = image size × magnification” — That would make the real object bigger than its picture. Divide instead.

7. MT1 · Apply

Model answer. The grain is 24 mm ÷ 8 mm = 3 scale bars wide on the photograph. Each bar is 10 µm, so the grain is 3 × 10 µm = 30 µm wide. (Or: magnification = 8 mm ÷ 0.010 mm = ×800; actual = 24 mm ÷ 800 = 0.03 mm = 30 µm.)

Checked automatically

• Actual width: 30 µm (within ±2%)
  • Common wrong answer 240 : You multiplied 24 by 10. First find how many scale bars fit across the grain: 24 ÷ 8.

A full answer includes

• 24 mm ÷ 8 mm = 3 scale bars.
• 3 × 10 µm = 30 µm.

Also accept

• 30 µm

Watch for

• “The grain is 24 µm because it is 24 mm on the photo.” — The photo is enlarged: use the scale bar to find how many times.