The amount of extension in an elastic spring varies directly as the a weight hung on it. If weight of 150 gm produces an extension of 2.9 cm, then what weight would produce an extension of 17.4 cm?

Explanation

`150` produces a `2.9` cm extension
Then `1` cm would be extended by `150/2.9` gm of weight.
∴ `1` cm will be extended by `51.72` gm of weight.
To produce an extension of `17.4` cm, `51.72 xx 17.4` gm of weight will be needed.
Therefore to produce an extension of `17.4` cm, `900` gm of weight will be needed.