2. Last year, an earthworm from Wigan named Dave wriggled into the record books as the largest found in the UK. Dave was $40 \mathrm{~cm}$ long and had a mass of $26 \mathrm{~g}$.
What was Dave's mass per unit length?
A $0.6 \mathrm{~g} / \mathrm{cm}$
B $0.65 \mathrm{~g} / \mathrm{cm}$
C $0.75 \mathrm{~g} / \mathrm{cm}$
D $1.6 \mathrm{~g} / \mathrm{cm}$
E $1.75 \mathrm{~g} / \mathrm{cm}$
SOLUTION
B

Dave's mass per unit length is $\frac{26}{40} \mathrm{~g} / \mathrm{cm}$. We have
$$
\frac{26}{40}=\frac{26}{10 \times 4}=\frac{2.6}{4}=0.65 \text {. }
$$

Therefore Dave's mass per unit length is $0.65 \mathrm{~g} / \mathrm{cm}$.