If a positive number represents above sea level and a negative number represents below sea level, (a) use a directed number to represent each of the following situations: (i) 15 m above sea level, (ii) 10 m below sea level: (b) describe the meaning of ‘-21 m’.

we are given that

a positive number represents above sea level and a negative number represents below sea level

(A)

(i)

15 m above sea level means positive number

so, that number would be +15m

(ii)

10 m below sea level means negative number

so, that number would be -10m

(B)

"-21m"

Since, sign is negative

so, it will be below sea level

so, 21m below sea levelAnswer