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Y_Kistochka [10]

3 years ago

9

Sum of 1+3+5+7+...+997

1 answer:

PilotLPTM [1.2K]3 years ago

4 0

1 + 3 + 5 + 7 + ... + 997

1, 3, 7, ... , 997 are terms of an arithmetic sequence

$a_1=1;\ a_2=3;\ ...;\ a_n=997\\\\d=a_2-a_1\to d=3-1=2\\\\a_n=a_1+(n-1)d\\\\subtitute\\\\997=1+(n-1)\cdot2\\977=1+2n-2\\977=2n-1\ \ \ \ |add\ 1\ to\ both\ sides\\2n=998\ \ \ \ |divide\ both\ sides\ by\ 2\\n=499\\\\S_n=\dfrac{a_1+a_n}{2}\cdot n\\\\subtitute:\ a_1=1;\ a_n=997;\ n=499\\\\S_{499}=\dfrac{1+997}{2}\cdot499=\dfrac{998}{2}\cdot499=499\cdot499=249,001$

Answer: 1 + 3 + 5 + 7 + ... + 997 = 249,001.

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ms shah grades 3402 math problems during 5th period this is 54% of the total number of problems she need to grade what is the to

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The total number of problems she needs to grade is 6.

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Last year, Maria had $10,000 to invest. She invested some of it in an account that paid 6% simple interest per year, and she inv

denis-greek [22]

Answer:

$3,000 invested at 6%

$7,000 invested at 10%

Step-by-step explanation:

Maria had total $10,000 to invest.

Let x be the amount that Maria invested initially at 6% interest rate.

0.06x

Then she invested the remaining amount at 10% interest rate.

0.10(10,000 - x)

She received a total of $880 in interest.

0.06x + 0.10(10,000 - x) = 880

0.06x + 1000 - 0.10x = 880

-0.04x = 880 - 1000

-0.04x = -120

0.04x = 120

x = 120/0.04

x = $3,000

This is the amount that Maria invested initially at 6% interest rate.

The remaining amount is

10,000 - 3,000

$7,000

This is the remaining amount that she invested at 10% interest rate.

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3 years ago

Find the missing terms of the geometric sequence.

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3 years ago

How do you simplify this?<br>x²y+xy² / y²+2/5 × xy

polet [3.4K]

$\huge \boxed{\mathbb{QUESTION} \downarrow}$

How do you simplify this?
x²y+xy² / y²+2/5 × xy

$\large \boxed{\mathbb{ANSWER\: WITH\: EXPLANATION} \downarrow}$

$\sf\frac{ { x }^{ 2 } y+x { y }^{ 2 } }{ { y }^{ 2 } + \frac{ 2 }{ 5 } \times xy } \\$

Factor the expressions that are not already factored.

_____

<u>How </u><u>to</u><u> factorise</u><u> </u><u>:</u><u>-</u>

<u>NUMERATOR</u> $\downarrow$

$\sf \: x ^ { 2 } y + x y ^ { 2 }$

Factor out xy.

$\sf \: xy\left(x+y\right)$

<u>DENOMINATOR</u> $\downarrow$

$\sf{ y }^{ 2 } + \frac{ 2 }{ 5 } \times xy \\$

Factor out 1/5.

$\sf \: {\frac{1}{5}y\left(2x+5y\right)} \\$

_____

Continuing...

$\sf\frac{xy\left(x+y\right)}{\frac{1}{5}y\left(2x+5y\right)} \\$

Cancel out y in both the numerator and denominator.

$\sf\frac{x\left(x+y\right)}{\frac{1}{5}\left(2x+5y\right)} \\$

Expand the expression.

$\sf\frac{x^{2}+xy}{\frac{2}{5}x+y} \\$

This can further simplified to as $\downarrow$

$= \boxed{\boxed{\bf\frac{5x\left(x +y\right)}{2x+5y}}}$

3 0

3 years ago