Video Transcript
Liam read 75 pages of a book in one day, and on the next day he read 18 pages. How many pages did he read in the two days?
The two important facts that we need to highlight in this problem are the number of pages that Liam reads on two different days. We’re told that he reads 75 pages of a book on one day and 18 pages on another day. And, the question asks us to calculate the number of pages that Liam reads in the two days. In other words, we need to add the two together to find the total. We need to find the answer to 75 plus 18.
75 is a number that’s made up of seven 10s and five ones. And, 18 is made up of one 10 and eight ones. We can start by finding out how many ones we have altogether. 75 has five ones and we need to add another eight ones. Five, six, seven, eight, nine, 10, 11, 12, 13. Five plus eight equals 13. But, how can we write 13 ones in the ones place? We can only fit one digit in each place. What if we exchange 10 of our ones for one 10?
Here we go there. Five plus eight equals 13. Now, let’s add the number of 10s together. There are seven 10s in 75 plus one 10 in 18, and we’ve got one 10 that we’ve exchanged. So, we need to find the answer to seven plus one plus one. Seven plus one equals eight plus another one equals nine. Our answer contains nine 10s and three ones.
We found the answer by adding the ones first. We have five ones in 75 and eight ones in 18. Five plus eight equals 13. We decided that 13 was too large to write in the ones column, so we exchanged 10 of our 13 ones for one 10. Then, we added up all the 10s we had. 75 contains seven 10s, and 18 contains one 10. We also exchanged the 10 so we have to add that too. This made a total of nine 10s. If Liam reads 75 pages of book in one day, and the next day he reads 18 pages, in total he reads 93 pages over the two days.
