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The ratio of the radius and height of a cone is 3:4. Its volume is 375737\frac{5}{7} cm³. The slant height of the cone is

Solution

✅ Correct Option: 3

The ratio of radius to height is 3:43:4, and the volume is 375737\frac{5}{7} cm³.

Let the radius be r=3xr = 3x and height be h=4xh = 4x for some constant xx.


Converting the mixed fraction to an improper fraction:

3757=37×7+5737\frac{5}{7} = \frac{37 \times 7 + 5}{7}

=259+57= \frac{259 + 5}{7}

=2647= \frac{264}{7} cm³


The volume of a cone is given by V=13πr2hV = \frac{1}{3}\pi r^2 h.

Substituting the values with π=227\pi = \frac{22}{7}:

2647=13×227×(3x)2×4x\frac{264}{7} = \frac{1}{3} \times \frac{22}{7} \times (3x)^2 \times 4x

2647=13×227×9x2×4x\frac{264}{7} = \frac{1}{3} \times \frac{22}{7} \times 9x^2 \times 4x

2647=13×227×36x3\frac{264}{7} = \frac{1}{3} \times \frac{22}{7} \times 36x^3

2647=227×12x3\frac{264}{7} = \frac{22}{7} \times 12x^3

2647=2647×x3\frac{264}{7} = \frac{264}{7} \times x^3

x3=1x^3 = 1

x=1x = 1 cm


The actual dimensions are:

Radius =3x=3×1=3= 3x = 3 \times 1 = 3 cm

Height =4x=4×1=4= 4x = 4 \times 1 = 4 cm


The slant height forms the hypotenuse of a right triangle with the radius and height.

Using the Pythagorean theorem:

l=r2+h2l = \sqrt{r^2 + h^2}

l=32+42l = \sqrt{3^2 + 4^2}

l=9+16l = \sqrt{9 + 16}

l=25l = \sqrt{25}

l=5l = 5 cm

Therefore, the slant height of the cone is 55 cm.

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