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Standard X

Mathematics

Volume of a Frustum

The mass of a...

Question

The mass of a uniform copper bar varies directly as its length. If a bar $40 c m$ long has a mass of approximately $420 g$ , find the mass of a bar $136 c m$ long.

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Solution

Mass $α$ length

$m α l$

$m = k l$

'k' is constant

Mass of $40$ cm long bar is $420$ grams

$420 = k \times 40$

$k = \frac{420}{40}$

$k = \frac{21}{2}$

$m = \frac{21}{2} l$ .

Now we have to find a mass of $136$ cm long bar

$m = \frac{21}{2} \times 136$

$m = 21 \times 68$

$m = 1428$

The mass of bar is $1428$ grams.

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The mass of a uniform copper bar varies directly as its length. If a bar 40 cm long has a mass of approximately 420 g, find the mass of a bar 136 cm long.

Mass α lengthmαlm=kl'k' is constantMass of 40 cm long bar is 420 grams420=k×40k=42040k=212m=212l.Now we have to find a mass of 136 cm long barm=212×136m=21×68m=1428The mass of bar is 1428 grams.

The mass of a uniform copper bar varies directly as its length. If a bar $40 c m$ long has a mass of approximately $420 g$ , find the mass of a bar $136 c m$ long.