Solve the exercise using the substitutive property:
21×31×21=
Let's solve this problem step-by-step:
- Step 1: Multiply the numerators of the fractions. We have 1×1×1=1.
- Step 2: Multiply the denominators of the fractions. We have 2×3×2=12.
- Step 3: Combine the results to form a fraction: 121.
- Step 4: Simplify the fraction if possible. Since the fraction 121 is already in its simplest form, no further simplification is needed.
Thus, the product of 21×31×21 is 121.
The correct answer choice is 121, matching choice 4.
Therefore, the solution to the problem is 121.