Kelsey turned 25 in 1999. Her older sister was born 3 years before Kelsey. It's currently 2021. How old is Kelsey's older sister? Give the rationale and then the answer.
Let's think step by step. Kelsey turned 25 in 1999 so she was born in 1999 - 25 = 1974. Kelsey's sister is older by 3 years so she was born in 1974 - 3 = 1971. It's currently 2021 and Kelsey's sister was born in 1971 so she is 2021 - 1971 = 50 years old.. The answer is: 50.

Gwendolyn can read 200 sentences of a book in 1 hour. She just brought a book from the library, having 20 paragraphs per page. What's the total time Gwendolyn will take to read the book if each paragraph has 10 sentences and the book has 50 pages? Give the rationale and then the answer.
Let's think step by step. Gwendolyn just brought a book from the library, having 20 paragraphs per page, and since the book has 50 pages, the number of paragraphs in the book is 50 * 20 = 1000 paragraphs. If each paragraph has 10 sentences, the book's number of sentences is 1000 * 10 = 10000 sentences. Since Gwendolyn can read 200 sentences of a book in 1 hour, she will read 10000 sentences in 10000 / 200 = 50 hours.. The answer is: 50.

Hannah's AdBlock blocks all but 20% of ads, and 20% of the ads it doesn't block are actually interesting. What percentage of ads aren't interested and don't get blocked? Give the rationale and then the answer.
Let's think step by step. First find the percentage of ads that aren't interesting: 100% - 20% = 80%. Then multiply that percentage by the percentage of ads that don't get blocked to find the percentage of ads that meet both criteria: 80% * 20% = 16%.. The answer is: 16.