The sum of the lengths of projections of $\mathrm{p} \hat{i}+\mathrm{q} \hat{j}+\mathrm{rk}$ on the…
The sum of the lengths of projections of $\mathrm{p} \hat{i}+\mathrm{q} \hat{j}+\mathrm{rk}$ on the co-ordinate axes, where $p=4, q=-5, r=7$ is
6 units
16 units
20 units
28 units
Solution
The projection on the $\mathrm{x}$-axis $=|\mathrm{p}|=4$
The projection on the $\mathrm{y}$-axis $=|\mathrm{q}|=5$
The projection on the $\mathrm{z}$-axis $=|\mathrm{r}|=7$
Sum $=4+5+7=16$