Overestimating and Underestimating: A increases by 2 million while B decreases by 2 m

doubleuson

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Oct 10, 2018
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Hi guys!

Really simple statistics percentage problem, but I'm having one of those brainfart moments:

So the original question states:

A increases by 2 million while B decreases by 2 million.

However, new information suggests the rise A was under-estimated by 11%, and the fall in B was overestimated by 26%, what is the net increase between the two?

My math suggests the answer should be a net increase of 740 000 (2 000 000*1.11 = 2 220 000; 2 000 000*0.74 = 1 480 000; 2 220 000 - 1 480 000 = 740 000).

Can someone reassure me I am right or suggest why I am wrong. I am getting confused as to whether I should multiple by 1 + % for underestimates and multiple by 0 - % for underestimates.
 
Hi guys!

Really simple statistics percentage problem, but I'm having one of those brainfart moments:

So the original question states:

A increases by 2 million while B decreases by 2 million.

However, new information suggests the rise A was under-estimated by 11%, and the fall in B was overestimated by 26%, what is the net increase between the two?

My math suggests the answer should be a net increase of 740 000 (2 000 000*1.11 = 2 220 000; 2 000 000*0.74 = 1 480 000; 2 220 000 - 1 480 000 = 740 000).

Can someone reassure me I am right or suggest why I am wrong. I am getting confused as to whether I should multiple by 1 + % for underestimates and multiple by 0 - % for underestimates.
What were the original sizes of A and B?
 
I am getting confused as to whether I should multiple by 1 + % for underestimates and multiple by 0 - % for underestimates.

If you want to increase an amount by a % you multiply by 1 + %/100, if decrease, by 1 - %/100. Your calculations appear to be correct.
 
A increases by 2 million while B decreases by 2 million.

However, new information suggests the rise A was under-estimated by 11%, and the fall in B was overestimated by 26%, what is the net increase between the two?

My math suggests the answer should be a net increase of 740 000 (2 000 000*1.11 = 2 220 000; 2 000 000*0.74 = 1 480 000; 2 220 000 - 1 480 000 = 740 000).

Can someone reassure me I am right or suggest why I am wrong. I am getting confused as to whether I should multiple by 1 + % for underestimates and multiple by 0 - % for underestimates.

If A was underestimated by 11%, that means the estimate of 2,000,000 is 11% less than the actual rise. The actual rise is not 11% more than the estimate. Do you see the difference?

I have to say that the question is misleading, as it doesn't clearly state that the 2 million is an estimate.
 
If A was underestimated by 11%, that means the estimate of 2,000,000 is 11% less than the actual rise. The actual rise is not 11% more than the estimate. Do you see the difference?

I have to say that the question is misleading, as it doesn't clearly state that the 2 million is an estimate.

Yes, this interpretation makes more sense.
 
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