Solve question no. 1 of page no. 75 from the chapter "Average" of textbook "Shaping Maths AB 5B Part I - Solutions".

a)
1.25 + 3.5 + 15.35 + 11.6 = 31.7
 

Press $\boxed{\mathrm{C}}$ 1.25 $\boxed{+}$ 3.5 $\boxed{+}$ 15.35 $\boxed{+}$ 11.6 $\boxed{=}$ Display: 31.7

The sum is 31.7 m.

b)
15.52 + 15.69 + 15.83 + 16.44 + 16.66 + 18.59 = 98.73
 

Press $\boxed{\mathrm{C}}$ 15.52 $\boxed{+}$ 15.69 $\boxed{+}$ 15.83 $\boxed{+}$ 16.44 $\boxed{+}$ 16.66 $\boxed{+}$ 18.59 $\boxed{=}$ Display: 98.73

The sum is 98.73 s.

c)
158.75 $÷$ 5 = 31.75
 

Press $\boxed{\mathrm{C}}$ 158.75 $\boxed{÷}$ 5 $\boxed{=}$ Display: 31.75

$158.75 $÷$ 5 = $31.75

d)
$7\frac{1}{4}$ + $9\frac{3}{5}$ + $6\frac{4}{5}$ + $8\frac{3}{4}$ = $30\frac{12}{5}$
 

Press $\boxed{\mathrm{C}}$ $7\frac{1}{4}$ $\boxed{+}$ $9\frac{3}{5}$ $\boxed{+}$ $6\frac{4}{5}$ $\boxed{+}$ $8\frac{3}{4}$ $\boxed{=}$ Display: $30\frac{12}{5}$

e)
33.88 $÷$ 11 = 3.08
 

Press $\boxed{\mathrm{C}}$ 33.88 $\boxed{÷}$ 11 $\boxed{=}$ Display: 3.08

f)

$2\frac{3}{4}$ h	=	2 h + $\frac{3}{4}$ h
	=	2 h + $\frac{3}{4}\times 60$ min
	=	2  h  45  min