Can you lookup the value in a key-value array with the value in an entry field? This might be impossible, but can you lookup a value in a key-value array with the value in a craft entry field? And perform math with it in twig? I'm trying to simplify my template code.

I have a key value array like so

{%
set aspectRatioSetting = {
    'four_three' : '0.75',
    'three_two' : '0.666666666667',
    'sixteen_nine' : '0.5625',
    'one_one' : '1'
} %}


And I'd like to be able to use those values in a math operation, the specific value looked up by a value in a custom entry field.

{% set transformParams = { width: 1250, height: 1250 * aspectRatioSetting.four_three } %}


where the value of the "four_three" key in the array is used in the math operation. Only the specific key would be set by the value in an entry field.

{% set transformParams = { width: 1250, height: 1250 * aspectRatioSetting.(entry.aspectRatio) } %}


There's not a good way for me to type it up because this clearly doesn't work. I'm just wondering if it's somehow possible. 

Or maybe I'm just overcomplicating things in an attempt to simplify things : /
Two options here ...

{% set transformParams = { width: 1250, height: 1250 * aspectRatioSetting[entry.aspectRatio] } %}


Or just give the select field a value that represents the number, not the word. So set a value of 0.75 instead of four_three, and let the label be Four/Three (or whatever seems fit).