Determine the Main Scale Reading (MSR).

The zero mark of the Vernier scale is past $8.6\,\text{cm}$ on the main scale.

$$\text{MSR} = 8.6\,\text{cm}$$

The $7^{\text{th}}$ mark on the Vernier scale aligns perfectly with a mark on the main scale.

$$\text{VSC} = 7$$

The least count (LC) of a standard Vernier caliper is $0.01\,\text{cm}$.

$$\text{Total Reading} = \text{MSR} + (\text{VSC} \times \text{LC})$$ $$\text{Total Reading} = 8.6\,\text{cm} + (7 \times 0.01\,\text{cm})$$ $$\text{Total Reading} = 8.6\,\text{cm} + 0.07\,\text{cm}$$ $$\text{Total Reading} = \boxed{\text{8.67}\,\text{cm}}$$

Q1b: Vernier Caliper Reading

The zero mark of the Vernier scale is past $60.4\,\text{cm}$ on the main scale.

$$\text{MSR} = 60.4\,\text{cm}$$

The $2^{\text{nd}}$ mark on the Vernier scale aligns perfectly with a mark on the main scale.

$$\text{VSC} = 2$$

The least count (LC) of a standard Vernier caliper is $0.01\,\text{cm}$.

$$\text{Total Reading} = \text{MSR} + (\text{VSC} \times \text{LC})$$ $$\text{Total Reading} = 60.4\,\text{cm} + (2 \times 0.01\,\text{cm})$$ $$\text{Total Reading} = 60.4\,\text{cm} + 0.02\,\text{cm}$$ $$\text{Total Reading} = \boxed{\text{60.42}\,\text{cm}}$$

Micrometer Screw Gauge Reading

The edge of the thimble is past the $5.5\,\text{mm}$ mark on the main scale (the $5\,\text{mm}$ mark and the $0.5\,\text{mm}$ mark after it are visible).

$$\text{MSR} = 5.5\,\text{mm}$$

The $12^{\text{th}}$ mark on the thimble scale aligns with the datum line.

$$\text{TSC} = 12$$

The least count (LC) of a standard micrometer screw gauge is $0.01\,\text{mm}$.

$$\text{Total Reading} = \text{MSR} + (\text{TSC} \times \text{LC})$$ $$\text{Total Reading} = 5.5\,\text{mm} + (12 \times 0.01\,\text{mm})$$ $$\text{Total Reading} = 5.5\,\text{mm} + 0.12\,\text{mm}$$ $$\text{Total Reading} = \boxed{\text{5.62}\,\text{mm}}$$