The value of n needed to make the equation true. n+19=40

Mathematics

2 answers:

dezoksy [38]3 years ago

7 0

Answer: n = 21

Step-by-step explanation: When you're asked to solve for n in an equation, what your really being asked to do is to get x by itself on one side of the equation.

In this problem, since 19 is being added to n, in order to get n by itself, we must subtract 19 from the left side of the equation and when we subtract 19 from the left side of the equation, remember that we must also subtract 19 from the right side of the equation.

So on the left, +19 and -19 cancel eachother out and

on the right, 40 - 19 is 21 so n = 21.

We can check our answer by substituting

a 21 back into the original equation.

So we have (21) + 19 = 40 or 40 = 40.

Schach [20]3 years ago

6 0

Answer:

n = 21

Step-by-step explanation:

Given

n + 19 = 40 ( subtract 19 from both sides )

n = 40 - 19 = 21

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in 2009 a total of R36 000 was invested in two accounts. One account earned 7% annual interest and the other earned 9% .The tota

Akimi4 [234]

a = amount invested at 7%

b = amount invested at 9%

we know the amount invested was ₹36000, thus we know that whatever "a" and "b" are, a + b = 36000. We can also say that

$\begin{array}{|c|ll} \cline{1-1} \textit{a\% of b}\\ \cline{1-1} \\ \left( \cfrac{a}{100} \right)\cdot b \\\\ \cline{1-1} \end{array}~\hspace{5em}\stackrel{\textit{7\% of a}}{\left( \cfrac{7}{100} \right)a}\implies 0.07a~\hfill \stackrel{\textit{9\% of b}}{\left( \cfrac{7}{100} \right)b}\implies 0.09b$

since we know the interest earned from the invested was ₹2920, then we say that 0.07a + 0.09b = 2920.

$\begin{cases} a + b = 36000\\\\ 0.07a+0.09b=2920 \end{cases} \\\\[-0.35em] ~\dotfill\\\\ \stackrel{\textit{using the 1st equation}}{a + b = 36000\implies \underline{b = 36000-a}}~\hfill \stackrel{\textit{substituting on the 2nd equation}}{0.07a~~ + ~~0.09(\underline{36000-a})~~ = ~~2920} \\\\\\ 0.07a+3240-0.09a=2920\implies 3240-0.02a=2920\implies -0.02a=-320 \\\\\\ a=\cfrac{-320}{-0.02}\implies \boxed{a=16000}~\hfill \boxed{\stackrel{36000~~ - ~~16000}{20000=b}}$