MediumMathematicsHigh School (9–10)Mensuration › Areas and PerimetersNumericalBoard Exam SAT

A metal washer has an outer radius of 3.5 cm and a round hole of radius 1.4 cm…

Try it on paper first. A hint, the key idea and the worked solution are here when you need them.

A metal washer has an outer radius of $3.5\ \text{cm}$ and a round hole of radius $1.4\ \text{cm}$ . Find the area of one face of the washer. Take $\pi = \dfrac{22}{7}$ .

Need a reminder? The key ideaShow

A ring has area $\pi(R^2 - r^2)$ . If a chord of the big circle touches the small circle, the area of the ring is $\pi \times (\text{half the chord})^2$ . A path outside a circle adds its width to the radius.

The worked solution

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Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.

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