# How much concrete is used on the island of Manhattan?

Case Interview case study hard Market sizing
Recent activity on Apr 03, 2018
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I'm interested in seeing a structure to a question that appears impossible/overwhelming , such as

"How much concrete is used on the island of Manhattan?"

How granular of a level is both reasonable for the interviewee and satisfactory as an answer for the interviewer?

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Hi Anonymous,

you can consider the following steps:

1. Identify where concrete is used; as besides buildings its main use is for bridges and other viability infrastructure, you could probably consider buildings only if the interviewer agrees
2. Estimate the number of districts of NY with concrete. You should not includes parks and other parts without buildings
3. Estimate the number of units using concrete per district – eg how many buildings per district
4. Estimate the amount of concrete per building as percentage of the total volume of the building walls
5. Multiply 2*3*4 for each segment identified in step 1

Best,

Francesco

Concrete is the most widely used manmade material on earth. 40 million tons of the stuff is poured every year and the world consumes 150 billion tons each year. The concrete used on the island of Manhattan weighs 900,000 tons. It would take 225 trucks to carry that much concrete with Slabjacking. The Empire State Building weighs 7,000,000 tons. How much concrete was used in the building?

To elaborate on other answer, for each block then you take an assumption of what is empty vs. Concrete volume by multiplying the width and length of block by the avg height of building and then assuming a “density factor” (I.e. how much space in a cubic meter is concrete vs. Empty) and then multiply by the number of blocks with the distinction of high vs low density.

Andrea

Hi,

• You can calculate the number of blocks (Streets an avenues on Manhattan) and the usage of concrete per block.
• I would split Manhattan blocks into 2 types with heavy (skyscrapers) and non-heavy construction and estimate the usage of concrete in each type of the blocks.
• Don't forget to subtract Central Park from the total number of blocks

Best

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