Ask question

Ask question

All categories

3 years ago

11

The base of a triangle is nine centimeters longer than the perpendicular height. If the area of the triangle is 180 square centi

meters, what is the length of the base, in centimeters?

1 answer:

Rom4ik [11]3 years ago

7 0

Answer:

<em>The base is 24 cm long.</em>

Step-by-step explanation:

<u>Equations</u>

Let's call

b= base of the triangle

h=height of the triangle

The base is 9 cm longer than the height, thus:

b = h + 9

The area of the triangle is:

$\displaystyle A=\frac{bh}{2}$

$\displaystyle A=\frac{(h+9)h}{2}$

And its value is 180:

$\displaystyle \frac{(h+9)h}{2}=180$

Multiplying by 2:

$(h+9)h=360$

Operating:

$h^2+9h-360=0$

Factoring:

$(h-15)(h+24)=0$

The only valid positive solution is:

h = 15 cm

And b = h + 9 = 24

b = 24 cm

The base is 24 cm long.

You might be interested in

Prove or disprove (from i=0 to n) sum([2i]^4) <= (4n)^4. If true use induction, else give the smallest value of n that it doe

ddd [48]

Answer:

The statement is true for every n between 0 and 77 and it is false for $n\geq 78$

Step-by-step explanation:

First, observe that, for n=0 and n=1 the statement is true:

For n=0: $\sum^{n}_{i=0} (2i)^4=0 \leq 0=(4n)^4$

For n=1: $\sum^{n}_{i=0} (2i)^4=16 \leq 256=(4n)^4$

From this point we will assume that $n\geq 2$

As we can see, $\sum^{n}_{i=0} (2i)^4=\sum^{n}_{i=0} 16i^4=16\sum^{n}_{i=0} i^4$ and $(4n)^4=256n^4$ . Then,

$\sum^{n}_{i=0} (2i)^4 \leq(4n)^4 \iff \sum^{n}_{i=0} i^4 \leq 16n^4$

Now, we will use the formula for the sum of the first 4th powers:

$\sum^{n}_{i=0} i^4=\frac{n^5}{5} +\frac{n^4}{2} +\frac{n^3}{3}-\frac{n}{30}=\frac{6n^5+15n^4+10n^3-n}{30}$

Therefore:

$\sum^{n}_{i=0} i^4 \leq 16n^4 \iff \frac{6n^5+15n^4+10n^3-n}{30} \leq 16n^4 \\\\ \iff 6n^5+10n^3-n \leq 465n^4 \iff 465n^4-6n^5-10n^3+n\geq 0$

and, because $n \geq 0$ ,

$465n^4-6n^5-10n^3+n\geq 0 \iff n(465n^3-6n^4-10n^2+1)\geq 0 \\\iff 465n^3-6n^4-10n^2+1\geq 0 \iff 465n^3-6n^4-10n^2\geq -1\\\iff n^2(465n-6n^2-10)\geq -1$

Observe that, because $n \geq 2$ and is an integer,

$n^2(465n-6n^2-10)\geq -1 \iff 465n-6n^2-10 \geq 0 \iff n(465-6n) \geq 10\\\iff 465-6n \geq 0 \iff n \leq \frac{465}{6}=\frac{155}{2}=77.5$

In concusion, the statement is true if and only if n is a non negative integer such that $n\leq 77$

So, 78 is the smallest value of n that does not satisfy the inequality.

Note: If you compute $(4n)^4- \sum^{n}_{i=0} (2i)^4$ for 77 and 78 you will obtain:

$(4n)^4- \sum^{n}_{i=0} (2i)^4=53810064$

$(4n)^4- \sum^{n}_{i=0} (2i)^4=-61754992$

7 0

3 years ago

Reggie read a 400 page book. In 5 days .On the first day , he read 120 pages . each day after that , he read the same number. Of

forsale [732]

400x5 divided by 120

4 0

3 years ago

Maria cut a trapezoid out of a large piece of felt. Tha trapezoid has a height of 9 cm and bases of 6 cm and 11 cm. What is the

stiks02 [169]

The area of Marcia's trapezoid felt is 76.5 sqaured centimeters

7 0

3 years ago

Read 2 more answers

Mumu + mumu=-----------

Morgarella [4.7K]

The answer is umu( M + m )

4 0

3 years ago

Extra points! Please help

Angelina_Jolie [31]

The answer to question 1 is B

the answer to question 2 is B

3 0

3 years ago

Read 2 more answers