11cm2s−1
22cm2s−1
33cm2s−1
44cm2s−1
Correct answer is B
With radius = 7cm, Area=πr2=227×72
= 154cm2
The next second, radius = 7.5cm, Area=πr2=227×7.52
= 176cm2
Change in area = (176−154)cm2=22cm2
∴ The rate of increase = 22cm^{2}s^{-1}
OR
Area (A) = \pi r^{2} \implies \frac{\mathrm d A}{\mathrm d r} = 2\pi r
Given \frac{\mathrm d r}{\mathrm d t} = 0.5
\frac{\mathrm d A}{\mathrm d r} \times \frac{\mathrm d r}{\mathrm d t} = \frac{\mathrm d A}{\mathrm d t}
\frac{\mathrm d A}{\mathrm d t} = 2\pi r \times 0.5 = 2 \times \frac{22}{7} \times 7 \times 0.5
= 22cm^{2}s^{-1}
The sales of five salesgirls on a certain day are as follows; GH¢ 26.00, GH¢ 39....
\alpha and \beta are the roots of the equation 2x^{2} - 3x + 4 = 0. Find \(\alpha + \bet...
Simplify \frac{9*3^{n+1} - 3^{n+2}}{3^{n+1} - 3^{n}}...
The roots of the quadratic equation 2x^{2} - 5x + m = 0 are \alpha and \beta, where m is...
Solve; \frac{P}{2} + \frac{k}{3} = 5 and 2p = k = 6 simultaneously...
If (x + 3) is a factor of the polynomial x^{3} + 3x^{2} + nx - 12, where n is a constant, find t...
Given that f(x) = \frac{x+1}{2}, find f^{1}(-2)....
The line y = mx - 3 is a tangent to the curve y = 1 - 3x + 2x^{3} at (1, 0). Find the value ...
The probability of Jide, Atu and Obu solving a given problem are \frac{1}{12}, \frac{1}{6} a...
A function f is defined by f :x→\frac{x + 2}{x - 3},x ≠ 3.Find the inverse of f&...