Answer:
20 m
Explanation:
Given:
- Length in mud = ¹/₂ its length
- Length in water = ¹/₃ its length
- Length above water = 3 ¹/₃ m
Let x be the length of the lamp post.
Convert 3 ¹/₃ to an improper fraction:
![\sf \implies 3 (1)/(3)=(3 * 3+1)/(3)=(10)/(3)](https://img.qammunity.org/2023/formulas/mathematics/high-school/fu2mbllasgop41bxp4weua8obggic0f54d.png)
The total length of the lamp post (x) is the sum of the three given lengths:
![\implies \sf mud+water+above\: water=x](https://img.qammunity.org/2023/formulas/mathematics/high-school/2j9bg2icz7eu5ce028715usm3fwm3ohv7c.png)
![\sf \implies (x)/(2)+(x)/(3)+(10)/(3)=x](https://img.qammunity.org/2023/formulas/mathematics/high-school/bl9rq8fr1lry0l1y7vgxv58v7n73npn48r.png)
Multiply both sides by 6:
![\sf \implies (6x)/(2)+(6x)/(3)+(6 \cdot 10)/(3)=6x](https://img.qammunity.org/2023/formulas/mathematics/high-school/n1p4em8b44h5dak67inddd50mfh3uk5leu.png)
![\sf \implies 3x+2x+20=6x](https://img.qammunity.org/2023/formulas/mathematics/high-school/xc3588h45qsmhs4lj7qnsfltm1a7sjxo6m.png)
![\sf \implies 5x+20=6x](https://img.qammunity.org/2023/formulas/mathematics/high-school/4ubjj0v57zp9wm5l4n86s9fdl6fnpidxzk.png)
Isolate x:
![\sf \implies 20=6x-5x](https://img.qammunity.org/2023/formulas/mathematics/high-school/tmctctf7gj9hc2yifm6m5umbrg1oxmma3w.png)
![\implies \sf x=20](https://img.qammunity.org/2023/formulas/mathematics/college/mhmvri98us74kcq9aj302t70921wdyc2sr.png)
Therefore, the whole length of the post is 20 m.