[The narrator reads out the onscreen text. Question3.]

NARRATOR: Three students in a city school carried out a survey to investigate whether or not the students in the school ate breakfast. Some of the data from this survey are included in the two-way table below.

[The three rows of the table are labelled "Eats breakfast regularly", "Does not eat breakfast regularly" and "Total". The three columns of the table are labelled "Male", "Female" and "Total". Figures in the table show that 410 females eat breakfast regularly, 300 males do not eat breakfast regularly, the total of males equals 620 and the total of people who do not eat breakfast regularly is 500. The other spaces in the table are blank.]

NARRATOR: For example, of the students surveyed, 410 females eat breakfast regularly. The total in row one is the sum of the number of male and female students surveyed who eat breakfast regularly. The total in column one is the total number of males in the survey, in this case 620. There are five cells in this two-way table that contain no entries. If we know two pieces of information in a row or column, we can find the third.

Considering column one. If 620 males were surveyed in total and 300 males don't eat breakfast regularly, that leaves 620 minus 300, so 320 males who do eat breakfast regularly.

Now considering row one. If there are 320 males that eat breakfast regularly and 410 females that also eat breakfast regularly, then there is a total of 320 plus 410, so 730 students who eat breakfast regularly.

Considering row two. If there are 500 students who don't eat breakfast regularly and 300 of them are male, then 500 minus 300, so 200 of them must be female.

Now considering column two. If there are 410 females that eat breakfast regularly and a further 200 females that don't eat breakfast regularly, then there must be a total of 410 plus 200, so 610 females.

Finally, we can complete the table by considering either the Totals row or the Totals column. Considering the Totals row, if there are 620 males and 610 females, then there is a total of 620 plus 610, so 1230 students.

Considering the Totals column. We see that if 730 students eat breakfast regularly and 500 students don't eat breakfast regularly, then there is a total of 730 plus 500, which again gives 1230 students.

The two-way table is now complete. As an example, we can see that out of 1230 students surveyed, 730 replied that they eat breakfast regularly, and 320 of those 730 were males.