Review question

# If we know the difference in their areas, how big are these sectors? Add to your resource collection Remove from your resource collection Add notes to this resource View your notes for this resource

Ref: R9423

## Suggestion

The figure shows two sectors in which $AB$, $CD$ are arcs of concentric circles, centre $O$ and radii $\quantity{2k}{cm}$ and $\quantity{3k}{cm}$ respectively. $A\hat{O}B$ is $\frac{3}{4}$ radian and the area $ABDC$ is $\quantity{30}{cm^2}$. Find

1. the value of $k$,

What are the areas of the two sectors in terms of $k$? Is there a formula we could use?

Is there a similar formula to help with finding arc lengths?