contestada

Lianna plays a card game in which she gets 5 points for every red card she draws but loses 10 points for every black card she draws. By the end of the game Lianna drew 7 times as many red card as black cards for a final total of 75 points. How many red cards did she drew during the game?

Respuesta :

If
R = number of red cards
B = number of black cards
then,
5*R = number of points earned from all red cards
-10*B = number of points lost from all black cards
5*R-10*B = total amount of points

This total is equal to 75 points (given)
5*R-10*B = 75

--------------------------------

We are told that "drew 7 times as many red card as black cards" so this means 
R = 7*B

Use substitution to find that...
5*R-10*B = 75
5*7*B-10*B = 75 ... R is replaced with 7*B
35*B-10*B = 75
25*B = 75
B = 75/25
B = 3

She selected 3 black cards

R = 7*B
R = 7*3
R = 21

and 21 red cards

Final Answer: 21

Otras preguntas