ADD power based on NRA/PRA

[tbearOD]

can someone help me figure out the theoretical add for a patient based on NRA/PRA

FCC: +1.75
Near Base: +1.75
NRA/PRA: +2.00/-0.50


the answer is +2.50 and I don't understand how/why

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[UnicornOpt]

NRA + PRA = Add

 

[odfuturedoc]

Here’s a better answer...
+2.00 -0.50 = +1.50
+1.50/2= +0.75
Final add = tentative add + adjustment
= +1.75 + 0.75
=+2.50