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Sliva [168]
2 years ago
13

numa prova de múltipla escolha com 30 questões, o aluno ganha 3 pontos por cada questão que acerta, mas perde 2 pontos por cada

questão que erra. Marcelo resolveu todas as questões dessa prova e conseguiu 50 pontos. Quantas questões ele acertou?
Mathematics
1 answer:
CaHeK987 [17]2 years ago
3 0

Answer:

Marcelo acertou 22 questões.

Step-by-step explanation:

Vamos representar

Questões que acerta = a

Questões que erra = b

a + b = 30 .......... Equação 1

a = 30 - b

o aluno ganha 3 pontos por cada questão que realizar, mas perde 2 pontos por cada questão que ocorrerá.

Matematicamente:

3 × a - 2 × b = 50

3a - 2b = 50 pontos ............. Equação 2

Substitua 30 - b por a na Equação 2

3 (30 - b) - 2b = 50

90 - 3b - 2b = 50

90 - 5b = 50

Colete termos semelhantes

90 - 50 = 5b

5b = 40

b = 40/5

b = 8

Questões que erra = b

Marcelo, portanto, perdeu 8 questões.

Dizem-nos que ele respondeu todas as 30 questões. Portanto, se ele perdeu 8 questões, o número de questões acertadas é representado pela Equação 1

a + b = 30 .......... Equação 1

a + 8 = 30

a = 30 - 8

a = 22 questões.

Portanto, ele acertou 22 questões.

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