You have 80 pennies.
Step-by-step explanation:
Given,
Number of coins = 150
Worth of coins = $7.80 = 7.80*100 = 780 cents
One penny = 1 cent
One dime = 10 cents
Let,
x be the number of pennies
y be the number of dimes
x+y=150 Eqn 1
x+10y=780 Eqn 2
Subtracting Eqn 1 from Eqn 2
[tex](x+10y)-(x+y)=780-150\\x+10y-x-y=630\\9y=630[/tex]
Dividing both sides by 9
[tex]\frac{9y}{9}=\frac{630}{9}\\y=70[/tex]
Putting y=70 in Eqn 1
[tex]x+70=150\\x=150-70\\x=80[/tex]
You have 80 pennies.
Keywords: linear equation, elimination method
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