Simon bought audio items and gives their approximate costs P

Simon bought audio items and gives their approximate costs. Prices up to lira 15 are given to the nearest lira 1. Prices over lira 15 are given to the nearest lira 5. Simon bought a CD player, and costing lira 12 and headphones costing lira 10 He says that he paid lira 150 in total This total is given to the nearest lira 10. Find the maximum possible price which Simon could have paid for me CD player You must price which show your working. A floodlight tower is marked with the following sign. The spotlights on the tower are rated at 2500 watts each. The manufacture can only guarantee that the wattage of these spotlights is accurate to the nearest 100 watts. What is the maximum number of spotlights that can safely be put on the lower? The formula W =I^2 R connects W(watts), I (amps) and R (ohms). For one of the spotlights, the value of l is 25 amps measured to 2 significant figures. What is the minimum possible value of R?

Solution

Max. wattage = 400,000 watts

a) Each spotlight = 2500 watts

No. of spotlights = 400000/2500 = 160 spotlights

b) W = I^2R

R = W/I^2 = 2500/25^2 = 4 ohm