5 km = 5000 m

S length =ab

= 1.8*5000

=9000 square meters

S step =(a+b)h/2

=(200+350)* 100/2

=550* 100/2

=55000/2

=27500 square meters

27500/9000 is approximately equal to 3. 1 (hour).

A: It takes about 3. 1 hour.

p97 2

S triangle =ah/2

= 1.2*5/2

=6/2

=3(㎡)

S length =ab

=4*5

=20(㎡)

S wall =s triangle +s length

=3+20

=23(㎡)

23* 185=4255 (block)

A: 4,255 bricks were used.

Right? If not, tell me what the problem is.