The speed of sound (shockwave) in an explosion is 100mph. How many seconds does the shockwave reach 2km away?​

Can someone me my sister? she is in third grade. 50 points and brainlist! ones that are not answered. plz and thx!

News cameras take an overhead picture of a crowd at an outdoor event journalist then count the total number of people in the picture and use the sample of estimate the total number of people in the crowd this process is an example of

Rachel reads 1/5 of the pages of a book plus 12 pages on the first day. on the second day, she reads 1/4 of the remaining pages plus 15 pages. on the third day, she reads 1/3 of the remaining pages plus 18 pages. on the fourth day, she reads the remaining 70 pages. how many total pages are in the book?