Answer:
d
Step-by-step explanation:
because
Multiply both sides of the second equation by 100 to get rid of the decimals:
0.05<em>n</em> + 0.10<em>d</em> = 1.50
==> 5<em>n</em> + 10<em>d</em> = 150
Multiply both sides of the first equation by -5:
<em>n</em> + <em>d</em> = 21
==> -5<em>n</em> - 5<em>d</em> = -105
Add the two equations together:
(5<em>n</em> + 10<em>d</em>) + (-5<em>n</em> - 5<em>d</em>) = 150 + (-105)
Notice that the terms containing <em>n</em> get eliminated and we can solve for <em>d</em> :
(5<em>n</em> - 5<em>n</em>) + (10<em>d</em> - 5<em>d</em>) = 150 - 105
5<em>d</em> = 45
<em>d</em> = 45/5 = 9
Plug this into either original equation to solve for <em>n</em>. Doing this with the first equation is easiest:
<em>n</em> + 9 = 21
<em>n</em> = 21 - 9 = 12
So Donna used 12 nickels and 9 dimes.
An integer is a rational number; 1/2 is a rational ratio with a denominator of 1; 0.4545 is a rational decimal; 0.44 is a irrational decimal and 0 is a rational whole numbers.
<h3>What is the difference between a rational and a irrational number?</h3>
The category irrational number can be applied to numbers that cannot be expresses as ratios or fractions. This includes decimals that do not terminate and are not repeating such as 0.44454...
<h3>On the other hand, rational numbers will include different types of numbers such as:</h3>
Integers: This refers to numbers that are not expressed as fractions.
Rational decimals: This includes repeating decimals such as 0.4545...
Rational ratios: This includes numbers such as 1/2 or 1/4.
Rational whole numbers such as 0,1,2, etc.
Learn more about rational numbers in: brainly.com/question/17450097
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It's the first one you can just add or multiply the expressions to get the answer
