James is revising for his upcoming maths exam.
During dinner, James decided to quiz his family on one of the questions that came up in his mock exam at school.
He asked:
How many 5 – digit even numbers less than 80 000 can be made with the digits
1 , 4 , 5 , 7 and 9
with no repetition of any digit?
Are you able to work out the answer?
Answer:
The last digit has to be 4 as this is the only number divisible by 2.
There is therefore a choice of 3 for the first number (as it can’t be 9 and the 4 is known as the last digit)
There is then a choice of 3 for the second number, a choice of 2 for the third number and the fourth will be the remaining number (so choice of 1).
Therefore, using the Product Rule:
3 x 3 x 2 x 1 x 1 = 18