The total if all 236 coins were nickels would be $11.80, which is $3.95 short of the actual amount.
Replacing a nickel with a dime adds $0.05 to the total value, so there must have been $3.95/$0.05 = 79 such replacements.
There are 79 dimes.
There are 236 -79 = 157 nickels.
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Using the given variables, the problem statement gives rise to two equations. One is the based on the number of coins. The other is based on their value.
- n + d = 236
- .05n +.10d = 15.75
Solving the first for n, we get
... n = 236 - d
Substituting that into the second equation, we have
... .05(236 -d) +.10d = 15.75
... .05d = 15.75 -236·.05 . . . . . collect terms, subtract .05·236
... d = 3.95/.05 . . . . . . . . . . . . . divide by .05
... d = 79
... n = 236-79 = 157
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The solution should look familiar, as it matches the verbal description at the beginning.
1) Data:
Meal calories consumed
Breakfast 400 cal
Lunch 350 cal
Dinner x
------------------
Total 400 + 350 + x = 750 + x
2) Equation: <span>
She consumes 2/3 of her daily calories at dinner => (2/3)[750+x] = x
3) Analyze each statement:
</span><span>a) Lena
consumed 1500 cal at dinner.
Solve the equation to find if the statement is true:
</span>
<span><span>(2/3)[750+x] = x</span>
2(750+x) = 3x
1500 + 2x = 3x
1500 = 3x - 2x
x = 1500
Conclusión: TRUE stament.
b) Do you equation 2/3 (x+400+350)=x can be
used to model the situation.
That is the same equation that I found above.
Conclusion: TRUE statement
c) Lena consumed 500 cal at dinner.
She consumed (2/3) * 1500 = 500 cal
Conclusion: TRUE statement
d) Lena
consumed 1000 cal at dinner.
No, we calculated that she consumed 500 cal at dinner.
Conclusion: FALSE statement
e) The equation 2/3(x)=x(400+350) can be used
to model the situation.
No: (2/3) x = 500 and x(400+350) = 500*750 = 375,00, which are not equal.
Conclusion: FALSE statement.
f) The equation 2/3x(400+350)=x Can’t be used to
model the situation
No: in that equation the variable x cancels out because it appears a factor at both sides.
</span>Conclusion: TRUE statement
"Congruent" should finish your sentence and make it a true statement.
