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.
Answer:
Step-by-step explanation:
There are 20 ballots, 8 have drawn a car the rest are white.
Find the probability to extract at least one ballot with the drawing of a car if not replaced:
1. If a ballot is taken out:
8 have drawn a car: thus we have 8/20 = 2/5
2. If two ballots are removed, probability of extracting 1 ballot with drawing of car is 8/20 leaving 7 out of 19 remaining. The 7/19 is the probability of drawing out a second ballot with the drawing of a car. Thus we have
8/20 * 7/19 = 56/380 = 14/95
3. If three ballots are removed, probability of extracting 1 ballot with drawing of car is 8/20 leaving 7 out of 19 remaining. The 7/19 is the probability of drawing out a second ballot with the drawing of a car leaving 6 out of 18 remaining. The 6/18 is the probability of drawing out a third ballot with the drawing of a car.
8/20 * 7/19 * 6/18 = 42/855
Answer: the answer is 2.75 because
Step-by-step explanation: 1.25+0.75+0.75=2.75 hope i Helped mark me as brainliest
