Discussion about math, puzzles, games and fun. Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ π -¹ ² ³ °

You are not logged in.

- Topics: Active | Unanswered

**paulc****Member**- Registered: 2014-02-05
- Posts: 1

I am trying to work out an average room height in a loft area, got so far and hit a barrier

73% of the roof is 1.65m high & 27% of the roof is 2.35m high, average is ? just going for a strong coffee

Offline

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 92,930

Hi paulc;

I would do it like this.

or simply

**In mathematics, you don't understand things. You just get used to them.**

**I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.**

Offline

**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,787

hi Paulc,

Welcome to the forum.

got so far and hit a barrier

That happens to me all the time when I go up in the loft. It has a sloping roof.

Bob

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

Offline

**Shishkin****Member**- Registered: 2014-02-26
- Posts: 2

I haven't done much maths for years and was never much good at averages. How do I work out this problem? After 15 games, Ben's average score was 17. After 20 games, his average increased to 21. What was Ben's average number of points per game in the last 5 games?

Offline

**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,787

hi Shishkin

Welcome to the forum.

To do this you need to work backwards to the total scores.

Av of 17 in 15 games means the total was 17 x 15

Av of 21 in 20 games means the total was 21 x 20

By subtracting one from the other you will get the score in the 5 new games. Then divide by 5.

Hope that helps.

Bob

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

Offline

**Shishkin****Member**- Registered: 2014-02-26
- Posts: 2

Thank you very much Bob!

Offline

**unamckee22****Member**- Registered: 2014-03-09
- Posts: 1

I am stuck on a question

I have three pieces of wood and my average is 0.23 I get one more piece of wood and my average is 0.14 .how long was the piece of wood you bought.

Offline

**ShivamS****Member**- Registered: 2011-02-07
- Posts: 3,640

Let a, b, c be the wood pieces you have and let d be the piece you bought.

(a+b+c)/3=0.23

a+b+c=0.69

(a+b+c+d)/4=0.14

a+b+c+d=0.56

a+b+c+d-a-b-c=0.56-0.69=-0.13

The piece of wood you bought was -0.13 units long (doesn't really make sense).

*Last edited by ShivamS (2014-03-09 10:37:33)*

Offline

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 92,930

Hi;

He probably meant .24 was the new average.

**In mathematics, you don't understand things. You just get used to them.**

**I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.**

Offline