A bag contains black beads and white beads in the ratio 7:4.

There are 42 black beads in the bag.

Work out how many beads there are altogether in the bag.

Step-by-step explanation:

Ratio of black to white = 7:4

Total ratio = 7 + 4 = 11

Let the total number of beads be y

Number of black bead = 42

: 7/11 * y = 42

7y/11 = 42

Cross multiply

7y = 42*11

7y = 462

y = 462/7

y = 66

Total beads is 66