When working with probabilities why is it sometimes necessary to add and sometimes to multiply?
Whether you need to add or multiply depends on whether it is a case of 'AND' or 'OR'. For 'AND' you multiply, and for 'OR' you add. Below are examples of each case, using dice as an example: To calculate the probability that I get a six on my first roll AND get a five on my second roll, I need to multiply: 1/6 x 1/6 = 1/36To calculate the probability that I get either a six OR a five on my first roll, I need to add: 1/6 + 1/6 = 2/6 = 1/3
MW
Related Maths GCSE answers
All answers ▸Find the two points of intersection of the graphs y=x2 and y=x+2.
The width of a rectangle is X cm. The length is 1·5 cm more than the width. The perimeter of the rectangle is 17 cm. Write down an equation satisfied by X and solve it to find X.
You and your brother have your pocket money split in the ratio 2:7. If your brother receives £42, how much do you receive?
Use factorisation to simplify the following expression (x^2-9)/(x^2-4x+3)