3. A bridge is built across a river. One quarter of the bridge is over the left bank of the river and one third of the bridge is over the right bank. The river is $120 \mathrm{~m}$ wide. How long is the bridge?
A $150 \mathrm{~m}$
B $190 \mathrm{~m}$
C $240 \mathrm{~m}$
D $288 \mathrm{~m}$
E $324 \mathrm{~m}$
3. D The river is $120 \mathrm{~m}$ wide and represents $\left(1-\frac{1}{4}-\frac{1}{3}\right)=\frac{5}{12}$ of the length of the bridge. Therefore $\frac{1}{12}$ of the length of the bridge is $24 \mathrm{~m}$. Hence the total length of the bridge is $12 \times 24 \mathrm{~m}=288 \mathrm{~m}$.