Answer: 5 groups, with each group containing 3 sopranos and 4 altos.
Step-by-step explanation:
In order to find the answer, we need to use GCD.
To find the GCD, we can list the factors of each number:
Factors of 15: 1, 3, 5, 15
Factors of 20: 1, 2, 4, 5, 10, 20
The common factors are 1 and 5. The greatest common divisor is 5. This means that the teacher can form a maximum of 5 groups with an equal number of sopranos and altos.
To distribute the singers evenly among the groups, the teacher would divide the total number of sopranos (15) and altos (20) by the number of groups (5).
Each group would consist of 3 sopranos (15 ÷ 5) and 4 altos (20 ÷ 5).
Therefore, the choir teacher can make a maximum of 5 groups, with each group containing 3 sopranos and 4 altos.