Nikka has a 100 stamp collection. Thirty-five percent of her stamps are Chinese, 20% are US stamps, and the rest are Japanese stamps. How many Japanese stamps does Nikka have? Give the rationale and then the answer.
Let's think step by step. Nikka has 100 x 35 / 100 = 35 Chinese stamps. She has 100 x 20 / 100 = 20 US stamps. So, Nikka has 35 + 20 = 55 stamps that are not Japanese. Thus, Nikka has 100 - 55 = 45 Japanese stamps.. The answer is: 45.

Jonsey is awake for 2/3 of the day and spends 1/2 her time awake playing outside and the rest inside. Her brother, Riley, is awake for 3/4 of the day and spends 1/3 of his day outside and the rest inside. How much time, on average, do they spend inside? Give the rationale and then the answer.
Let's think step by step. Jonsey is awake for 16 hours because 24 x (2 / 3) = 16. Jonsey spends 1 / 2 her day inside because 1 - (1 / 2) = 1 / 2. Jonsey spend 8 hours inside because 16 x (1 / 2) = 8. Riley is awake for 18 hours because 24 x (3 / 4) = 18. Riley spends 2 / 3 of his day inside because 1 - (1 / 3) = 2 / 3. Riley spends 12 hours inside because 18 x (2 / 3) = 12. In total they spend 20 hours inside because 8 + 12 = 20. On average, they spend 10 hours inside because 20 / 2 = 10.. The answer is: 10.

Chrystal's vehicle speed is 30 miles per hour. Ascending the mountain decreases its speed by fifty percent, and descending the mountain increases its speed by twenty percent. If the distance going to the top of the mountain is 60 miles and the distance going down to the foot of the mountain is 72 miles, how many hours will Crystal have to pass the whole mountain? Give the rationale and then the answer.
Let's think step by step. The vehicle's speed decreases to 30 x 0.50 = 15 miles per hour when ascending to the top of the mountain. So, the total time Crystal will have to spend going to the top of the mountain is 60 / 15 = 4 hours. And the speed of the vehicle increases by 30 x 0.20 = 6 miles per hour when going down to the foot of the mountain. So, the total speed of the vehicle when going down is 30 + 6 = 36 miles per hour. Thus, Chrystal will have to spend 72 / 36 = 2 hours to descend from the mountain. Therefore, the total hours she will spend to pass the whole mountain is 4 + 2 = 6 hours.. The answer is: 6.