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Question Number 183457 by Acem last updated on 26/Dec/22

He went to work by his car at speed 120 km/hr   and back home the same way 90 km/hr, find the   average speed for the entire distance traveled.

$${He}\:{went}\:{to}\:{work}\:{by}\:{his}\:{car}\:{at}\:{speed}\:\mathrm{120}\:{km}/{hr} \\ $$$$\:{and}\:{back}\:{home}\:{the}\:{same}\:{way}\:\mathrm{90}\:{km}/{hr},\:{find}\:{the} \\ $$$$\:{average}\:{speed}\:{for}\:{the}\:{entire}\:{distance}\:{traveled}. \\ $$$$ \\ $$

Answered by Matica last updated on 26/Dec/22

$$ \\ $$

Commented by Matica last updated on 26/Dec/22

Commented by Acem last updated on 26/Dec/22

Thx Mr! correct, and it′s better rounded it to close   number such 102.857 is closer to 103. Thank you

$${Thx}\:{Mr}!\:{correct},\:{and}\:{it}'{s}\:{better}\:{rounded}\:{it}\:{to}\:{close} \\ $$$$\:{number}\:{such}\:\mathrm{102}.\mathrm{857}\:{is}\:{closer}\:{to}\:\mathrm{103}.\:{Thank}\:{you} \\ $$

Answered by mr W last updated on 26/Dec/22

v_(total) =((2d)/((d/v_1 )+(d/v_2 )))=((2v_1 v_2 )/(v_1 +v_2 ))           =((2×120×90)/(120+90))≈103 km/h

$${v}_{{total}} =\frac{\mathrm{2}{d}}{\frac{{d}}{{v}_{\mathrm{1}} }+\frac{{d}}{{v}_{\mathrm{2}} }}=\frac{\mathrm{2}{v}_{\mathrm{1}} {v}_{\mathrm{2}} }{{v}_{\mathrm{1}} +{v}_{\mathrm{2}} } \\ $$$$\:\:\:\:\:\:\:\:\:=\frac{\mathrm{2}×\mathrm{120}×\mathrm{90}}{\mathrm{120}+\mathrm{90}}\approx\mathrm{103}\:{km}/{h} \\ $$

Commented by Acem last updated on 26/Dec/22

Thanks Mr!

$${Thanks}\:{Mr}! \\ $$

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