A bag contains 40 marbles. The probability of selecting a red marble at random is 1/5. How many red marbles are in the bag?

8 red marbles.

Step-by-step explanation:

All together we have 40 marbles. The fraction of marbles that are red is 1/5 which means that we should divide the total number of marbles, which is 40 by the denominator ( Bottom number of fraction ) 5 so that we get the number of groups that have 1 red marble in them. In this case we have 8 groups.

40/5=8

You always divide by the denominator ( Bottom number of fraction ) first and then you multiply your answer by the numerator ( Top number of fraction ) .

If each group has 1 red marble in it and we have 8 groups, it means that we have 8 red marbles in the bag.

1 * 8 = 8 red marbles in the bag

If the numerator (number above the fraction line) was more than one, then this would mean that we have more than 1 marble in each group of marbles.

Example:

If we had 3/5 we would have 3 marbles in each group of marbles. This means that instead of doing 1 * 8 we would have to do 3 * 8 = 24. We would have 24 red marbles in the bag.

Easy and quick way if you do not need the explanation:

Another way we could do this is by simply multiplying the fraction ( 1/5 ) by the total number of marbles ( 40 ). This would still give us an answer of 8 red marbles in the bag. 40/5=8, 8*1=8

(sin 42)/31. = sinx)/37

sinx = 37 (sin42)/31

= 37× 0.66/31 = 0.787

x= 51.9

other angle opposite to y = 180-51.9-42

= 180- 93.9 =86.1

so

sin42)/31 = sin 86.1)/y

0.021 = 0.997 /y

y= 0.997/0.021 =47.47