Johnetta simplified 7/9+ 3/8 her work is shown below. identify where she made an error

jok3333 [9.3K]

The first answer is 2
The Second is 8
The third is, if the w changes then the p would change as well resulting to multiplication

Hope this helps!!!

6 0

2 years ago

. A box in a certain supply room contains four 40-W lightbulbs, five 60-W bulbs, and six 75-W bulbs. Suppose that three bulbs ar

yaroslaw [1]

Answer:

a) 59.34%

b) 44.82%

c) 26.37%

d) 4.19%

Step-by-step explanation:

(a)

There are in total 4+5+6 = 15 bulbs. If we want to select 3 randomly there are K ways of doing this, where K is the combination of 15 elements taken 3 at a time

$K=\binom{15}{3}=\frac{15!}{3!(15-3)!}=\frac{15!}{3!12!}=\frac{15.14.13}{6}=455$

As there are 9 non 75-W bulbs, by the fundamental rule of counting, there are 6*5*9 = 270 ways of selecting 3 bulbs with exactly two 75-W bulbs.

So, the probability of selecting exactly 2 bulbs of 75 W is

$\frac{270}{455}=0.5934=59.34\%$

(b)

The probability of selecting three 40-W bulbs is

$\frac{4*3*2}{455}=0.0527=5.27\%$

The probability of selecting three 60-W bulbs is

$\frac{5*4*3}{455}=0.1318=13.18\%$

The probability of selecting three 75-W bulbs is

$\frac{6*5*4}{455}=0.2637=26.37\%$

Since the events are disjoint, the probability of taking 3 bulbs of the same kind is the sum 0.0527+0.1318+0.2637 = 0.4482 = 44.82%

(c)

There are 6*5*4 ways of selecting one bulb of each type, so the probability of selecting 3 bulbs of each type is

$\frac{6*5*4}{455}=0.2637=26.37\%$

(d)

The probability that it is necessary to examine at least six bulbs until a 75-W bulb is found, supposing there is no replacement, is the same as the probability of taking 5 bulbs one after another without replacement and none of them is 75-W.

As there are 15 bulbs and 9 of them are not 75-W, the probability a non 75-W bulb is $\frac{9}{15}=0.6$

Since there are no replacement, the probability of taking a second non 75-W bulb is now $\frac{8}{14}=0.5714$

Following this procedure 5 times, we find the probabilities

$\frac{9}{15},\frac{8}{14},\frac{7}{13},\frac{6}{12},\frac{5}{11}$

which are

0.6, 0.5714, 0.5384, 0.5, 0.4545

As the events are independent, the probability of choosing 5 non 75-W bulbs is the product

0.6*0.5714*0.5384*0.5*0.4545 = 0.0419 = 4.19%

3 0

3 years ago

Peyton's field hockey team wins 4 games out of every 7 games played. Her team lost 9 games. How many games did Peyton's team pla

andre [41]

Answer:

Games played= 21 games

Step-by-step explanation:

Giving the following information:

Peyton's field hockey team wins 4 games out of every 7 games played.

We know that Peyton's team loses 3 games out of 7.

So if the team lost 9 games, the proportion is completed 3 times.

Games played= 3*7= 21 games

4 0

3 years ago

P P,Q and R can finish a task in 8, 10 and 12 hours respectivly.They started working together but after 3 hours, P and R left. H

zimovet [89]

Answer:

45 minutes

Step-by-step explanation:

Assume task completed in total x hours

$\frac{x}{10} + \frac{3}{8} + \frac{3}{12} = 1 \\ 12x + 45 + 30 = 120 \\ 12x = 45 \\ x = \frac{15}{4} = 3 \frac{3}{4}$

So q will take 45 more minutes

7 0

2 years ago

A clock has a diameter of 16 inches. Which measurement is closest to the area of the clock in square inches? 804.25 in2 50.27 in

meriva

Answer:

200.96 in2

Step-by-step explanation:

Area of a circle = nr²

n = 3.14

r = radius

the diameter is the straight line that passes through the centre of a circle and touches the two edges of the circle.

A radius is half of the diameter

diameter = 2r

radius = 16 inches / 2 = 8 in

Area = 3.14 x 8² = 200.96 in²

3 0

2 years ago