Question

A.Mary wrote all the integers from 1 to 19. How many numbers did she write?

Answer 1

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