You are Here: Home >< Maths

# Exam question understanding - help.

Announcements Posted on
TSR's new app is coming! Sign up here to try it first >> 17-10-2016
1. Hi,

This is for my biology practice paper, and I may work this out myself in due time, but I'm sat here trying to workout this maths question on it. I have the answer in-front of me - but I cannot see how you get to this figure. Can someone explain it to me?

Doctors investigated the accuracy of two methods, A and B, used to measure sperm counts.They obtained samples of semen from 500 men. They used both methods to obtain a spermcount for each sample.
• Method A required the semen to be diluted by a factor of 2 before counting.• Method B required dilution by a factor of 20.

Method B involved counting the number of sperm cells seen in small squares on aspecial glass microscope slide. Each square contained 0.25 × 10^–6 cm3 semen. Forone diluted sample of semen, the mean number of sperm cells per square was 1.05.Calculate the mean number of sperm cells per cm3 of semen. Show your working

Probably won't get a question like this on my exam paper - but I would feel the better for having a firmer understanding on the working-out.
2. It's okay - I worked it out.

Divide - 1/0.25 × 10^–6 cm3 ...x 20. Then x 1.05. = 84 x 10^6.

It's because I hadn't figured out the first division.

It's a shame I wouldn't get 20-mins in an exam to get my head around this...but then again, it is 7am. (need more coffee, perhaps).

## Register

Thanks for posting! You just need to create an account in order to submit the post
1. this can't be left blank
2. this can't be left blank
3. this can't be left blank

6 characters or longer with both numbers and letters is safer

4. this can't be left empty
1. Oops, you need to agree to our Ts&Cs to register

Updated: June 14, 2016
TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Today on TSR

### How does exam reform affect you?

From GCSE to A level, it's all changing

Poll
Useful resources

### Maths Forum posting guidelines

Not sure where to post? Read here first

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams

## Groups associated with this forum:

View associated groups
Study resources

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.