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    Subject

    Quantitative Aptitude

    Topic

    Areas & Volumes

    Wheels of diameters 7cm and 14cm start rolling simultaneously from x & y which are 1980 cm apart towards each other in opposite directions. Both of them make the same number of revolutions per second. If both of them meet after 10seconds.The speed of the smaller wheel is

    ক)
    22m/s
    খ)
    33m/s
    গ)
    44m/s
    ঘ)
    55m/s

    Explanation

    let each wheel make x revolutions per sec. Then [(2π∗72∗x)+(2π∗7∗x)]∗10=1980\left[\left(2\mathrm\pi\ast\frac72\ast\mathrm x\right)+\left(2\mathrm\pi\ast7\ast\mathrm x\right)\right]\ast10=1980 (2∗227∗72∗x)+(2∗227∗72∗x)=198\left(2\ast\frac{22}7\ast\frac72\ast x\right)+\left(2\ast\frac{22}7\ast\frac72\ast x\right)=198 66x=19866x=198 distance moved by smaller wheel in 3 revolutions 2∗227∗72∗3=66cm2\ast\frac{22}7\ast\frac72\ast3=66cm speed of smaller wheel = 663\frac{66}3 m/s = 22m/s

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