A 100 watt light bulb radiates energy at a rate of \( 100 \mathrm{~J} / \mathrm{s} \). (The watt, a unit of power or energy over fime, is cefined as \( 1 \mathrm{~J} / \mathrm{s} \).) if all of the light emitted has a wavelength of 505 nm , how many photons are emitted per second? Express your answer to three significant figures.

Solve for \( x \) and \( y \) simultaneously: \[ \begin{array}{l}x+2 y=22 \\ \text { and } \\ \qquad x y=36\end{array} \]

5) Find the constant term in the expansion of \( \left(x-\frac{2}{x^{2}}\right)^{6} \)

13. \( -6 \times(-6)=\square \)

2. A school planned to buy \( x \) calculators for a total cost of \( K \) sh 16200 . The supplier agreed to offer a discount of \( K \) sh 60 per calculator. The school was then able to get three extra calculators for the same amount of money. a. Write an expression in terms of \( x \) for the original price of each calculator ( 1 mark) b. Write an expression in terms of \( x \) for the price of each calculator after the discount (8mark) co Form an equation in \( x \) and hence determine the number of calculators the school boug ht (5 mar ks)

Divide these decimals. \( 200.57 / 31= \)