Question

The  ratio  of  white  marbles  to  black  marbles  was 2 / 3 . After 6 white marbles were removed and 6 black marbles were added,the new ratio was 1/2.How many white marbles were there at first ?

Answer 1

Gọi số bút trắng là a, bút đen là b

Ta có :

a = b x \(\frac{2}{3}\)

(a - 6) = (b + 6) x \(\frac{1}{2}\)

a - 6 = b x \(\frac{1}{2}\)+ 6 x \(\frac{1}{2}\)

a - 6 = b x \(\frac{1}{2}\)+ 3

b x \(\frac{2}{3}\)- 6 = b x \(\frac{1}{2}\)+ 3

b x \(\frac{2}{3}\)- b x \(\frac{1}{2}\)= 3 + 6

b x \(\frac{1}{6}\)= 9

b = 9 : \(\frac{1}{6}\)= 54

a = 54 x \(\frac{2}{3}\) = 36

Đáp số : 36 cái bút trắng

Answer 2

is twenty four marbles 

if my answer correct k for me 

Answer 3

you two made a mistakes