18) What percentage of numbers from 1 to 70 have 1 or 9 in the unit's digit?

Step 1: Identify the numbers from 1 to 70 that have 1 or 9 in the unit's digit.

Step 2: The numbers ending with 1 are 1, 11, 21, 31, 41, 51, 61. So, there are 7 numbers.

Step 3: The numbers ending with 9 are 9, 19, 29, 39, 49, 59, 69. So, there are also 7 numbers.

Step 4: Add the numbers from step 2 and step 3. So, 7 + 7 = 14 numbers have 1 or 9 in the unit's digit.

Step 5: To find the percentage, divide the total number of favorable outcomes by the total number of outcomes and multiply by 100.

Step 6: The total number of outcomes is 70 (since we are considering numbers from 1 to 70).

Step 7: So, the percentage is (14/70) * 100 = 20%.

Therefore, 20% of numbers from 1 to 70 have 1 or 9 in the unit's digit.