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3 years ago

How can you quickly calculate 20 percent of any bill amount?

Mathematics

2 answers:

il63 [147K]3 years ago

8 0

The answer is C an example is 20% of $20 is 4, so you would lose the zero and double the 2 to get 4

Radda [10]3 years ago

4 0

Answer:

C. Round the amount to the nearest $10, remove the zero in the ones place, and double the resulting amount.

Step-by-step explanation:

The percentage is quite present in our day to day, but still generates doubt and confusion at the time of doing the accounts. We use percentages to calculate discounts offered at stores, interest rates on financing, profits obtained from the sale of a particular product, etc.

An easy way to quickly calculate 20% of any invoice value is what is described in letter C.

For example: 20% of 100 dollars is 20 dollars. To calculate this quickly, you must remove the last zero from the number 100 and multiply the remainder by 2.

Removing the last zero from the number 100 will result in the number 10. Multiplying the number 10 by 2, the result will be 20. Thus, one can conclude that the 20% of 100 $ is 20 $.

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3 years ago

Three of these expressions are equal to the volume of the barn shown. Which expression is not?

timurjin [86]

The statement that does not match the others is the one at lower right.

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The barn's volume can be decomposed into a rectangular prism and a triangular one. Thus the upper right expression is a true represenation of the barn's volume:

... Volume of triangular prism + Volume of rectangular prism

The volume of a rectangular prism is the product of its dimensions. The dimensions of the rectangular prism portion of the barn's volume are a, b, c, so the volume of that portion is ...

... Volume of rectangular prism = a·b·c

The volume of a triangular prism is the area of the triangular base multiplied by the length of the prism. Here, the triangular base has base dimension b and height (d-c), so its area is ...

... Area of triangular barn end = (1/2)b(d-c)

Since the length of the barn is "a", the volume of the triangular prism is ...

... Volume of triangular prism = (1/2)b(d-c)a = (1/2)·a·b·(d-c)

The total volume is the sum of the volumes of the parts ...

... a·b·c + (1/2)·a·b·(d-c) . . . . . . matches the upper right selection

This can be factored by removing a·b to outside parentheses:

... a·b·((1/2)·(d-c) + c) . . . . . . . . . matches the lower left selection

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Since the two left selections match the one at upper right, the odd one is the one at lower left.

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3 years ago

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If $1,000 is invested at 4% simple interest, how much will the investment be worth after 2 years? Please explain how compound an

Novay_Z [31]

<h3>Answer:</h3>

simple interest: $1080.00
compounded annually: $1081.60

<h3>Step-by-step explanation:</h3>

Simple Interest

Simple interest is computed on the principal amount only. Each year, 4% of the principal is added to the balance. So, at the end of 2 years, the balance is ...

... $1000 + 0.04×$1000 + 0.04×$1000

... = $1000×(1 + 0.04×2) = $1000×1.08

... = $1080.00

_____

Comment on the computation

The added interest is the rate (per year) multiplied by the number of years. Here, that is 0.04×2×(principal amount). The formula for the simple interest earned is often seen as ...

... I = Prt . . . . . where I is the amount of interest, P is the principal amount, r is the interest rate for the time period, t is the number of time periods.

The account balance (A) with interest added is ...

... A = P + I = P + Prt

... A = P(1 +rt)

Here, the time period is years, and the rate given is an annual rate.

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Compound Interest

Compound interest is computed on the account balance at the beginning of the period, not just the principal amount. After the first period, the account balance includes interest earned so far. So, the interest is earning interest. That is why it is called compounded interest.

Here, the balance at the end of the first year is the principal amount plus the interest that has earned:

... $1000 + 0.04×$1000 = $1000×1.04 = $1040.00

The balance at the end of the second year when the interest is compounded is this account balance plus the interest it earns:

... $1040 + 0.04×$1040 = $1040×1.04 = $1081.60

You may notice that the intial principal, $1000, has been multiplied by the factor 1.04 twice. Using exponents, the multiplier for a period of 2 years is 1.04×1.04 = 1.04².

_____

Comment on the computation

The multiplier of the account balance each year is raised to a power that is the number of years. Here, the account balance at the end of 2 years is (1+0.04)² times the principal amount. A formula that is seen for this is ...

... A = P(1 +r)^t . . . . . where A is the final account balance, P is the principal amount, r is the interest rate for the time period, and t is the number of time periods.

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Answer:

Step-by-step explanation:

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