Answer:
A. She wrote 19 numbers
B. She wrote 12 numbers
C. She wrote 29 digits
Step-by-step explanation:
To find haw many numbers from x to y subtract x and y and then add 1
- Ex: There are 6 numbers from 1 to 6 because (6 - 1) + 1 = 6 (1, 2, 3, 4, 5, 6)
To find how many numbers between x and y subtract x and y then subtract 1
- Ex: There are 4 numbers between 1 and 6 because (6 - 1) - 1 = 4 (2, 3, 4, 5)
The numbers from 1 to 9 have one digit and from 10 to 99 have two digits
A.
∵ Mary wrote all the integers from 1 to 19
∵ (19 - 1) + 1 = 19
∴ She wrote 19 numbers
B.
∵ Rena wrote all the integers from 1 to 12
∵ (12 - 1) + 1 = 12
∴ She wrote 12 numbers
C.
∵ Mary wrote all the integers from 1 to 19
∵ From 1 to 9 the numbers have one digit
∵ There are 9 numbers from 1 to 9 because (9 - 1) + 1 = 9
∴ The number of digits from 1 to 9 = 9 × 1 = 9 digits
∵ There are 10 numbers from 10 to 19 because (19 - 10) + 1 = 10
∵ From 10 to 19 each number has 2 digits
∴ The number of digits from 10 to 19 = 10 × 2 = 20 digits
∴ The number of digits from 1 to 19 = 9 + 20 = 29 digits
∴ She wrote 29 digits
