Initially, ar = v.w

Now finally

a_r'  = v' 𝜔'

v' = v + 10% of v = 1.1 v

𝜔' = 𝜔 + 10% of 𝜔 = 1.1𝜔

a' = v'𝜔' = 1.1 v × 1.1 𝜔 = 1.21 v𝜔 = 1.21 a_r 

Then % change in a_r = $\frac{{\mathrm{a}}_{\mathrm{r}}^{\mathrm{\prime }}-{\mathrm{a}}_{\mathrm{r}}}{{\mathrm{a}}_{\mathrm{r}}}\times 100$ 

= $\frac{1.21{\mathrm{a}}_{\mathrm{r}}-{\mathrm{a}}_{\mathrm{r}}}{{\mathrm{a}}_{\mathrm{r}}}\times 100\mathrm{\%}$ 

= 0.21 × 100% = 21%