Ramina found the length of two pieces of ribbon to be 47.6 inches and 39.75 inches. Which is an effective estimation strategy for finding the sum of the two lengths? Round 39.75 to 30 and 47.6 to 40, then add. Round 39.75 to 40 and 47.6 to 48, then add. Add 47.6 and 39.75, then round the answer. Subtract 39.75 from 47.6, then round the answer.

(b) The correct strategy is : Round 39.75 to 40 and 47.6 to 48, then add.

Step-by-step explanation:

Here,

The length of the fist ribbon = 47.6 inches

The length of the second ribbon = 39.75 inch

Now, as the number 47.6 has digit 6 in its tenth place of decimal.

Also, 6 > 5, so 0. 6 is rounded off to 1.0

Hence, 47.6 is rounded off to 47 + 1.0 = 48

So, the rounded off length of the first ribbon = 48 inches

the number 39.75 has digits 75 in its tenth and hundredth place of decimal.

Also, 75 > 50, so 0. 75 is rounded off to 1.0

Hence, 39.75 is rounded off to 39 + 1.0 = 40

So, the rounded off length of the second ribbon = 40 inches

So, the sum of the two length = Sum of (First + Second) length

= 48 inches + 40 inches = 88 inches

Hence, the correct strategy is:

Round 39.75 to 40 and 47.6 to 48, then add.