What numbers does the square root of 355 fall between?

a) 15 and 16

b) 17 and 18

c) 18 and 19

d) 20 and 21

The answer is c) 18 and 19.

Let's go through all choices:

a) 15 and 16 is not correct because √355 > 16 > 15:

15 = √15² = √225

16 = √16² = √256

√355 > √256 > √225 ⇒ √355 > 16 > 15

b) 17 and 18 is not correct because √355 > 18 > 17:

17 = √17² = √289

18 = √18² = √324

√355 > √324 > √289 ⇒ 19 > √355 > 18

c) 15 and 16 is correct because:

18 = √18² = √324

19 = √19² = √361

√361 > √355 > √324 ⇒ 19 > √355 > 18

d) 20 and 21 is not correct because 21 > 20 > √355:

20 = √20² = √400

21 = √21² = √441

√441> √400> √355 ⇒ 21 > 20 > √355