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zzz [600]
2 years ago
11

Helene is finding the sum (9 + 10i) + (–8 + 11i). She rewrites the sum as (–8 + 11)i + (9 + 10)i. Which statement explains the p

roperty of addition that she made an error in using?
Mathematics
2 answers:
mr_godi [17]2 years ago
6 0

Answer:

Step-by-step explanation:

Given that Helene is finding the sum (9 + 10i) + (–8 + 11i).

Also given that She rewrites the sum as (–8 + 11)i + (9 + 10)i.

The mistake she did is in the second term distributing i.

(9+10i) is not equal to (9+10)i

Similarly (-8+11i) is not equal to (-8+11)i

The correct method she should have done is

grouping real terms together and imaginary terms together and finding the sum

(9 + 10i) + (–8 + 11i).\\=9+10i-8+11i\\=(9-8)+i(10+11)\\=1+21i

She made a mistake of taking out i from real term without changing the real term appropriately.

Thus she did the mistake of grouping unlike terms and factorising.

Ugo [173]2 years ago
4 0
The answer is that Helene incorrectly used the distributive property by combining the real number and the coefficient of the imaginary part.
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Serena estimates that she can paint 60 square feet of wall space every half -hour .Write a equations for the relationship with t
lina2011 [118]

Answer: So, the relationship with i hours as the indecent variables would be y=120i

Serena can't paint 400 square feet of wall space of wall space in 3.5 hours.

Step-by-step explanation:

Since we have given that

Area that she can paint = 60 square feet

Time taken = half hour = 30 minutes = 0.5 hours

Using "Unitary method, we get that

In 0.5 hours, she can paint = 60 square feet

In 1 hour, she can paint = \dfrac{60}{0.5}=120\ sq.\ feet

In i hours, she can paint = 120\times i\ sq.\ feet=120i\ sq.\ feet

Let the total area she can paint be 'y'.

So, the relationship with i hours as the indecent variables would be

y=120i

Now,  Can Serena paint 400 square feet of wall space i. 3.5 hours

We put y = 400 and i = 3.5 hours to check whether it is equal or not.

400= 120\times 3.5\\\\400\neq 420

Hence, Serena can't paint 400 square feet of wall space of wall space in 3.5 hours.

3 0
1 year ago
Lydia buys 5 pounds of apples and 3 pounds of bananas for a total of $8.50. Ari buys 3 pounds of apples and 2 pounds of bananas
Anarel [89]
5x + 3y= 8.50
3x + 2y= 5.25

Lydia is the first equation. She bought 5 pounds of apples which is x and bought 3 pounds of bananas which is y. Basically, remember each banana and apple weighs a price per pound. We don't know the price so we just put an x. This is the same for the second equation
8 0
2 years ago
Read 2 more answers
In an apartment complex with 28 units, 19 of the renters keep a pet. What percentage does not keep a pet?
Aleks04 [339]

If 19 out of 28 renters keep a pet, there are 28-19 = 9 renters who don't keep a pet.

Whenever you have a subset of some set, and you want to know which percentage of the set the subset represents, you simply have to compute

\dfrac{\text{number of elements in the subset}}{\text{number of elements in the set}}\times 100

So, in your case, you're wondering what percentage of 28 does 9 represent. So, the formula becomes

\dfrac{9}{28}\times 100 = 0.32\overline{142857}\times 100 = 32.\overline{142857} \approx 32.14\%

6 0
1 year ago
A university knows from historical data that 25% of students in an introductory statistics class withdraw before completing the
Vikki [24]

Answer:

13.4%

Step-by-step explanation:

Use binomial probability:

P = nCr p^r q^(n-r)

where n is the number of trials,

r is the number of successes,

p is the probability of success,

and q is the probability of failure (1-p).

Here, n = 16, r = 2, p = 0.25, and q = 0.75.

P = ₁₆C₂ (0.25)² (0.75)¹⁶⁻²

P = 120 (0.25)² (0.75)¹⁴

P = 0.134

There is a 13.4% probability that exactly 2 students will withdraw.

8 0
2 years ago
Lincoln Middle School has a total of $200 to spend on notebooks and tablets for the school board meeting. Notebooks cost $7 each
Anton [14]
The school can buy fifteen notebooks and nineteen tablets.  15X7=105 and 5X19=95.  95+105=200.  The first thing you want to do is realize that 5Xanything will give you an answer that has a 0 or a five at the end, so you want to find a product by 7 that ends with a 0 or 5 too.
4 0
2 years ago
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