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June 12th, 2018, 09:35 AM  #1 
Newbie Joined: Jun 2018 From: Jersey Posts: 3 Thanks: 0  Confusion on algebra question please help
Right so the question states that the volume of a triangular prism is 24cm cubed. it gave the length of the triangular prism as 5cm and the base of the cross sectional area 6. It wanted me to work out the height. So I converted it to algebra: (6*h/2) * 5 = 24cm^3 From there I went to: 6*h * 10 = 48cm^3 and from there I solved it down to h = 0.8cm However the answer is infact 1.6 cm (which agrees with all the other variables), the difference coming from the 10 being a five. My question is why on earth would the 5 stay a five when the entire equation must be multiplied by 2 to eliminate the /2??? Sorry if it's really obvious and I'm just not seeing it, thanks in advance. 
June 12th, 2018, 09:50 AM  #2 
Senior Member Joined: Aug 2012 Posts: 2,255 Thanks: 681 
If I give you 1/2 * 4 and I ask you to multiply that expression by 2, what do you get? 1/2 * 4 = 2, so multiplying by 2 gives you 4. If you multply 1/2 by 2 AND you multiply 4 by 2 you are in effect multiplying the whole expression by 4. It's already a multiplication. You are perhaps thinking that if it were 1/2 + 4 then you'd multiply both terms by 2. But when it's 1/2 x 4, you only want to multiply the expression by 2, once. 

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algebra, confusion, geometry, question, trigonometry 
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