To get 4 or fewer correct, at least 2 answers have to be wrong. And the probability of that is:
3/4 x 3/4=9/16
1-9/16=probability that 4 or fewer are correct=7/16 ☺☺☺☺
People should conserve energy because it produces a higher quality of life. Reduced emissions result in cleaner air quality. It also helps create a healthier planet and helps sustain resources we have.
Let's call the 13¢ stamps a and the 18¢ stamps b:
a+b = 42 and therefore a= 42-b (formula 1)
0.13a+0.18b= 6.66 In this formula, substitute the value of a according to formula 1:
0.13(42-b)+0.18b= 6.66 Multiply on the left to get rid of the parenthesis:
5.46-0.13b+0.18b= 6.66 Subtract 5.46 from both sides:
-0.13b+0.18b= 1.20 Add on the left:
0.05b= 1.20 Divide both sides by 0.05
b= 24 You have 24 18¢ stamps and:
42-24= 18 13¢ stamps
Check: (24 x 0.18) + (18 x 0.13)= 6.66 Correct.
Divide 1515 by 100 and you would get 15.15 the divide the .15 by 3 and and you will get 3.5 so the answer will be 15 3/5
