A gift box 20 cm long, 20 cm wide and 5 cm high At least how many centimeters of ribbon do you need?

A gift box 20 cm long, 20 cm wide and 5 cm high At least how many centimeters of ribbon do you need?

（20×2+20×2+5×4）×3+15
=（40+40+20）×3+15
=（80+20）×3+15
=100×3+15
=300+15
=315 (CM)
A: at least 315 cm ribbon is required

How much cement and river sand stone is needed for one side of C40 concrete?
With a side of C40 concrete, 32.5 cement, coarse sand and pea sand are used. How much cement, river sand and pea sand are needed? In order to enhance the strength of concrete, is coarse sand better or fine sand better,
The proportion of cement, sand and gravel is calculated in kilogram

Generally, the dosage of cement per cubic meter of C 40 concrete is about 500-550 kg, sand 800 kg and stone 1200 kg; the best sand is medium sand

Construction workers need to use cement, sand and stones to make 27 tons of concrete according to the mass ratio of 2:3:4. How many tons of cement, sand and stones do they need?
Note: 27 / 10 tons of concrete~

27 / 10 tons = 2.7 tons
Cement consumption: 2.7t * (2 / 9) = 0.6T
Sand consumption: 2.7t * (3 / 9) = 0.9t
Stone consumption: 2.7 tons * (4 / 9) = 1.2 tons