A collection of nickels and dimes is worth $4.40. There are 53 coins in all. How many nickels are there?

Nickel is a US coin worth 5 cents or 0.05.
Dime is a US coin worth 10 cents or 0.10

n + d = 53
0.05n + 0.10d = 4.40

n = 53 - d
0.05(53 - d) + 0.10d = 4.40
2.65 - 0.05d + 0.10d = 4.40
0.05d = 4.40 - 2.65
0.05d = 1.75
d = 1.75 / 0.05
d = 35

n = 53 - d
n = 53 - 35
n = 18

There are 18 nickels and 35 dimes.

0.05n + 0.10d = 4.40
0.05(18) + 0.10(35) = 4.40
0.90 + 3.5 = 4.40
4.40 = 4.40

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3 years ago

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The difference of the square of a number and 28 is equal to 3 times that number

Pepsi [2]

Answer:

- 4, 7

Step-by-step explanation:

Let the required number be x.

Therefore, according to the given condition:

${x}^{2} - 28 = 3x \\ {x}^{2} - 3x - 28 = 0 \\ {x}^{2} - 7x + 4x - 28 = 0 \\ x(x - 7) + 4(x - 7) = 0 \\ (x - 7)(x + 4) = 0 \\ x - 7 = 0 \: or \: x + 4 = 0 \\ x = 7 \: or \: x = - 4 \\$