Part (a)
For 1 plank

$I_1 = \dfrac{100(20^3)}{12}$
$I_1 = \frac{200\,000}{3} \, \text{mm}^4$

For the whole beam

$I = 6I_1 = 6(200\,000/3)$

$I = 400\,000 \, \text{mm}^4$

$\dfrac{M}{EI} = \dfrac{M_1}{E_1 I_1}$ where E_{1} = E

$\dfrac{M}{E(400\,000)} = \dfrac{M_1}{E(\frac{200\,000}{3})}$

$\dfrac{M_1}{M} = \dfrac{1}{6}$ *answer*

Part (b)

For 1 plank

$I_1 = \dfrac{100(10^3)}{12}$
$I_1 = \frac{25\,000}{3} \, \text{mm}^4$

For the whole beam

$I = 12I_1 = 12(25\,000/3)$

$I = 100\,000 \, \text{mm}^4$

$\dfrac{M}{EI} = \dfrac{M_1}{E_1 I_1}$ where E_{1} = E

$\dfrac{M}{E(100\,000)} = \dfrac{M_1}{E(\frac{200\,000}{3})}$

$\dfrac{M_1}{M} = \dfrac{1}{12}$ ) *answer*

## I think what is ask is the…

## Yes you are absolutely right…

In reply to I think what is ask is the… by Aerisk16

Yes you are absolutely right. We flagged this page for revision. Note that after revision is made, our comments will be put to archive. Thank you for calling our attention, highly appreciated.