7 Mathematic Questions

*DO NOT SAY I'M CHEATING, BECAUSE I'M NOT. I'M STUDYING FOR A HARD QUIZ COMING UP, AND THESE QUESTIONS ARE PRACTICE QUESTIONS. I'M ALLOWING PEOPLE TO ANSWER THEM SO I CAN CLARIFY THEM AND UNDERSTAND WHY YOU PICKED THE ANSWERS. DO NOT GUESS ON THE ANSWERS. DON'T BOTHER TO COMMENT SAYING I'M CHEATING, IF YOU DO I WILL REPORT YOU TO YAHOO! ANSWERS TO BLOCK OR BAN YOU ME.*

#1: Which ratios form a proportion?

A: 3/15, 12/55
B: 8/24, 12/35
C: 5/18, 25/90
D: 4/11, 16/25

#2: Which ratio forms a proportion with 9/15

A: 6/10
B: 16/21
C: 36/50
D: 45/70

#3: A textbook weighs 2/5 pounds. How many kilograms does the textbook weigh? Round your answer to the nearest tenth of a pound. 1kg ~ 2.2 lb

A: 1.1 kg
B: 1.8 kg
C: 5.5 kg
D: 4.7 kg

#4: Solve the proportion using number sense: 2/8 = x / 48


#5: Solve the proportion using cross products: 18/20 = k / 110


#6: Are the ratios 25/45 and 15/27 propotional? Explain.


#7: A 10-acre field produced 750 bushels of corn. At that rate, how much corn can be produced from a 14-acre field?

Dude,read my answer and LEARN how to solve these:
#1: if 2 ratios are equal ( form a proportion!) you can divide them with different numbers to make them a same ratio. Example : 4/10 , 6/15 if you divide both numbers in the 1st ratio to 2 you'll get 2/5 and also if you divide both numbers in the 2nd one to 3 you get 2/5 which is equal to the first 2/5 so these two ratios form a proportion!
the correct answer is C! if you divide the 2nd ratio by 5 you get 5/18 which is the first ratio!
(think of the ratio as a pizza which has pieces(slices) and you want to take some pieces,like in 5/8 you want to take 5 pieces of piazza from a 8 pieced (!) pizza!note that your pizza doesn't have to be sliced in to 8 pieces like real life,it can be anything!)
#2: the answer is A.why? if you divide the firsst ratio by 3 and divide ratio in A by 2,both of them give you 3/5!