You are here:

Advanced Math/Ratio / Proportion Follow-up

Advertisement


Question
One cubic foot of concrete contains the amounts for 1:2:4 and 1:2.5:5.  Maybe that will help.

Sorry for the omission.

Answer
"1125 ft³ of concrete is needed. 4/5 must be 1:2:4 concrete"
4/5 of 1125 ft³ = 900 ft³
You need 900 ft³ of 1:2:4 concrete.

0.22 ft³ cement, 0.44 ft³ sand, and 0.88 ft³ gravel is used to make 1 ft³ concrete.
900 ft³ concrete × 0.22 ft³ cement/(ft³ concrete) = 198 ft³ cement
198 ft³ cement is required

The sand:cement ratio is 2:1.
2 × cement = 2×198 ft³ = 396 ft³ sand
396 ft³ sand is required

The gravel:cement ratio is 4:1.
4 × cement = 4×198 = 792 ft³
792 ft³ gravel is required.  

Advanced Math

All Answers


Answers by Expert:


Ask Experts

Volunteer


Janet Yang

Expertise

I can answer questions in Algebra, Basic Math, Calculus, Differential Equations, Geometry, Number Theory, and Word Problems. I would not feel comfortable answering questions in Probability and Statistics or Topology because I have not studied these in depth.

Experience

I tutor students (fifth through twelfth grades) and am a Top Contributor on Yahoo!Answers with over 24,000 math solutions.

Publications
Co-author of An Outline of Scientific Writing: For Researchers With English as a Foreign Language

Education/Credentials
I have a Bachelor's degree in Applied Mathematics from the University of California at Berkeley.

Past/Present Clients
George White Elementary School. Homework Help program at the Ridgewood Public Library, Ridgewood, NJ. Individual students.

©2016 About.com. All rights reserved.