The total mass gap = 2400 g = 2.4 kg. Use a comparison bar model.<br><br>
[[model:questions/solutions/q4633.png]]<br><br>
&bull; Total mass = 69.7 kg, Gap = 2.4 kg<br>
&bull; Brian = (Total + Gap) ÷ 2 = (69.7 + 2.4) ÷ 2<br>
&bull; Brian = 72.1 ÷ 2 = 36.05 kg<br>
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Brian weighs 36.05 kg.<br>
Check: Alan = 36.05 - 2.4 = 33.65 kg. 36.05 + 33.65 = 69.7. ✓